Recent Publications
| Author | Title | Year | Journal/Proceedings | Reftype | DOI/URL |
|---|---|---|---|---|---|
| Guldin, S., Huttner, S., Tiwana, P., Orilall, M.C., Ulgut, B., Stefik, M., Docampo, P., Kolle, M., Divitini, G., Ducati, C., Redfern, S.A.T., Snaith, H.J., Wiesner, U., Eder, D. & Steiner, U. | Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO2 crystallisation | 2011 | Energy & Environmental Science Vol. 4(1), pp. 225-233 |
article | DOI |
| Abstract: Anatase TiO2 is typically a central component in high performance dye-sensitised solar cells (DSCs). This study demonstrates the benefits of high temperature synthesised mesoporous titania for the performance of solid-state DSCs. In contrast to earlier methods, the high temperature stability of mesoporous titania is enabled by the self-assembly of the amphiphilic block copolymer polyisoprene-block-polyethylene oxide (PI-b -PEO) which compartmentalises TiO2 crystallisation, preventing the collapse of porosity at temperatures up to 700 degrees C. The systematic study of the temperature dependence on DSC performance reveals a parameter trade-off: high temperature annealed anatase consisted of larger crystallites and had a higher conductivity, but this came at the expense of a reduced specific surface area. While the reduction in specific surface areas was found to be detrimental for liquid-electrolyte DSC performance, solid-state DSCs benefitted from the increased anatase conductivity and exhibited a performance increase by a factor of three. | |||||
BibTeX:
@article{Guldin2011,
author = {Guldin, S. and Huttner, S. and Tiwana, P. and Orilall, M. C. and Ulgut, B. and Stefik, M. and Docampo, P. and Kolle, M. and Divitini, G. and Ducati, C. and Redfern, S. A. T. and Snaith, H. J. and Wiesner, U. and Eder, D. and Steiner, U.},
title = {Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO2 crystallisation},
journal = {Energy & Environmental Science},
year = {2011},
volume = {4},
number = {1},
pages = {225--233},
doi = {http://dx.doi.org/10.1039/c0ee00362j}
}
|
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| Boucharef, M., Di Bin, C., Boumaza, M.S., Colas, M., Snaith, H.J., Ratier, B. & Boucle, J. | Solid-state dye-sensitized solar cells based on ZnO nanocrystals | 2010 | Nanotechnology Vol. 21(20) |
article | DOI |
| Abstract: We report on the development of solution-processed ZnO-based dye-sensitized solar cells. We fabricate mesoporous ZnO electrodes from sol-gel processed nanoparticles, which are subsequently sensitized with conventional ruthenium complexes and infiltrated with the solid-state hole transporter medium 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). Starting from ZnO nanorods synthesized from solution, we investigate the porous ZnO film morphology using various precursor formulations. The nature of the polymeric additive used in the initial ZnO formulation, as well as the ZnO electrode sintering treatment, is varied and its influence on device performance and charge dynamics, probed by transient perturbation techniques, is discussed. We show that using ethyl-cellulose in the initial ZnO formulation is responsible for an improved dye loading on the ZnO porous electrode, while a gradual sintering step at 350 degrees C is suitable for the proper removal of the organic phases that can be found in the ZnO films after their deposition by spin-coating. Using only 800 nm thick porous ZnO electrodes sensitized by N719, the best performing device exhibits a short-circuit current density of 2.43 mA cm(-2) under simulated solar emission of (100 mW cm(-2)), associated with an overall power conversion efficiency of 0.50%. | |||||
BibTeX:
@article{Boucharef2010,
author = {Boucharef, M. and Di Bin, C. and Boumaza, M. S. and Colas, M. and Snaith, H. J. and Ratier, B. and Boucle, J.},
title = {Solid-state dye-sensitized solar cells based on ZnO nanocrystals},
journal = {Nanotechnology},
year = {2010},
volume = {21},
number = {20},
doi = {http://dx.doi.org/10.1088/0957-4484/21/20/205203}
}
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| Boucle, J., Snaith, H.J. & Greenham, N.C. | Simple Approach to Hybrid Polymer/Porous Metal Oxide Solar Cells from Solution-Processed ZnO Nanocrystals | 2010 | Journal of Physical Chemistry C Vol. 114(8), pp. 3664-3674 |
article | DOI |
| Abstract: This work is devoted to the development of hybrid bulk heterojunction solar cells based on porous zinc oxide (ZnO) electrodes and poly(3-hexylthiophene) (P3HT), using simple synthesis procedures and deposition techniques. Starting from ZnO nanocrystals with well-controlled properties, porous ZnO electrodes of suitable porosity are deposited by spin-coating, varying the main experimental parameters such as composition of the initial ZnO formualtion and choice of the organic ligand. Significant charge transfer yields are observed in the corresponding solar cells, and the influence of processing conditions oil device performance is investigated using conventional techniques as well as transient photovoltage/photocurrent decay measurements. The temperature used to sinter the ZnO electrode is found to be specifically crucial to ensure efficient charge transport in the device while avoiding a loss in interfacial area through nanocrystal coalescence. Using 8 x 13 nm ZnO nanorods, the best device exhibits a power conversion efficiency of 0.35% under 100 mW.cm(-2) AM 1.5G simulated solar emission. This strategy, using processing in air with simple deposition techniques, competes with related approaches based on nanostructured ZnO processed using more complex procedures. Moreover, device performance and photophysics are found to be greatly influenced by the morphology of the starting ZnO nanocrystals, illustrating that fine control of the inorganic component call effectively tune the performance of hybrid bulk heterojunction solar cells. | |||||
BibTeX:
@article{Boucle2010,
author = {Boucle, J. and Snaith, H. J. and Greenham, N. C.},
title = {Simple Approach to Hybrid Polymer/Porous Metal Oxide Solar Cells from Solution-Processed ZnO Nanocrystals},
journal = {Journal of Physical Chemistry C},
year = {2010},
volume = {114},
number = {8},
pages = {3664--3674},
doi = {http://dx.doi.org/10.1021/jp909376f}
}
|
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| Docampo, P., Guldin, S., Stefik, M., Tiwana, P., Orilall, M.C., Huttner, S., Sai, H., Wiesner, U., Steiner, U. & Snaith, H.J. | Control of Solid-State Dye-Sensitized Solar Cell Performance by Block-Copolymer-Directed TiO2 Synthesis | 2010 | Advanced Functional Materials Vol. 20(11), pp. 1787-1796 |
article | DOI |
| Abstract: Hybrid dye-sensitized solar cells are typically composed of mesoporous titania (TiO2), light-harvesting dyes, and organic molecular hole-transporters. Correctly matching the electronic properties of the materials is critical to. ensure efficient device operation. In this study, TiO2 is synthesized in a well-defined morphological confinement that arises from the self-assembly of a diblock copolymer-poly(isoprene-b-ethylene oxide) (Pl-b-PEO). The crystallization environment, tuned by the inorganic (TiO2 mass) to organic (polymer) ratio, is shown to be a decisive factor in determining the distribution of sub-bandgap electronic states and the associated electronic function in solid-state dye-sensitized solar cells. Interestingly, the tuning of the sub-bandgap states does not appear to strongly influence the charge transport and recombination in the devices. However, increasing the depth and breadth of the density of sub-bandgap states correlates well with an increase in photocurrent generation, suggesting that a high density of these sub-bandgap states is critical for efficient photo-induced electron transfer and charge separation. | |||||
BibTeX:
@article{Docampo2010,
author = {Docampo, P. and Guldin, S. and Stefik, M. and Tiwana, P. and Orilall, M. C. and Huttner, S. and Sai, H. and Wiesner, U. and Steiner, U. and Snaith, H. J.},
title = {Control of Solid-State Dye-Sensitized Solar Cell Performance by Block-Copolymer-Directed TiO2 Synthesis},
journal = {Advanced Functional Materials},
year = {2010},
volume = {20},
number = {11},
pages = {1787--1796},
doi = {http://dx.doi.org/10.1002/adfm.200902089}
}
|
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| Driscoll, K., Fang, J.F., Humphry-Baker, N., Torres, T., Huck, W.T.S., Snaith, H.J. & Friend, R.H. | Enhanced Photoresponse in Solid-State Excitonic Solar Cells via Resonant Energy Transfer and Cascaded Charge Transfer from a Secondary Absorber | 2010 | Nano Letters Vol. 10(12), pp. 4981-4988 |
article | DOI |
| Abstract: We present a spiro linked molecule 2 2' 7 7' tetrakis(3 hexyl 5 (7 (4 hexylthlophen 2 yl)benzo[c][1 2 5]thiadiazol 4 4 yl)thiophen 2 yl) 9 9' spirobifluorene which acts as a secondary absorber in solid state excitonic solar cells Blending with a hole transpoting matenal 2 2'7 7'-tetrakis(N N di-p-methoxyphenyl amine) 9 9' spirobifluorene and used in conjunction with a near infrared dye (termed TTI) results in an extended spectral response which yields a notable increase in short circuit current and power conversion efficiency This enhancement is due to both exciton energy transfer and also nanoscale charge generation in the blend via the formation of an excited sate spiro complex with charge transfer character | |||||
BibTeX:
@article{Driscoll2010,
author = {Driscoll, K. and Fang, J. F. and Humphry-Baker, N. and Torres, T. and Huck, W. T. S. and Snaith, H. J. and Friend, R. H.},
title = {Enhanced Photoresponse in Solid-State Excitonic Solar Cells via Resonant Energy Transfer and Cascaded Charge Transfer from a Secondary Absorber},
journal = {Nano Letters},
year = {2010},
volume = {10},
number = {12},
pages = {4981--4988},
doi = {http://dx.doi.org/10.1021/nl103087s}
}
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| Kabra, D., Lu, L.P., Song, M.H., Snaith, H.J. & Friend, R.H. | Efficient Single-Layer Polymer Light-Emitting Diodes | 2010 | Advanced Materials Vol. 22(29), pp. 3194-+ |
article | DOI |
| Abstract: Single-layer polymer light-emitting diodes are fabricated using poly (9, 9'-dioctylfluorene)-co-benzothiadiazole (F8BT) as the emissive layer in contact with metal oxide injection layers ITO/ZnO/Cs2CO3/F8BT/MoO3/Au. Luminous efficiencies of up to 23 cd A(-1) are achieved for polymer layer thicknesses near 1 mu m. | |||||
BibTeX:
@article{Kabra2010,
author = {Kabra, D. and Lu, L. P. and Song, M. H. and Snaith, H. J. and Friend, R. H.},
title = {Efficient Single-Layer Polymer Light-Emitting Diodes},
journal = {Advanced Materials},
year = {2010},
volume = {22},
number = {29},
pages = {3194--+},
doi = {http://dx.doi.org/10.1002/adma.201000317}
}
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| Nedelcu, M., Guldin, S., Orilall, M.C., Lee, J., Huttner, S., Crossland, E.J.W., Warren, S.C., Ducati, C., Laity, P.R., Eder, D., Wiesner, U., Steiner, U. & Snaith, H.J. | Monolithic route to efficient dye-sensitized solar cells employing diblock copolymers for mesoporous TiO2 | 2010 | Journal of Materials Chemistry Vol. 20(7), pp. 1261-1268 |
article | DOI |
| Abstract: We present a material and device based study on the fabrication of mesoporous TiO2 and its integration into dye-sensitized solar cells. Poly(isoprene-block-ethyleneoxide) (PI-b-PEO) copolymers were used as structure directing agents for the sol-gel based synthesis of nanoporous monolithic TiO2 which was subsequently ground down to small particles and processed into a paste. The TiO2 synthesis and the formation of tens of micrometre thick films from the paste is a scalable approach for the manufacture of dye sensitised solar cells (DSCs). In this study, we followed the self-assembly of the material through the various processing stages of DSC manufacture. Since this approach enables high annealing temperatures while maintaining porosity, excellent crystallinity was achieved. Internal TiO2 structures ranging from the nanometre to micrometre scale combine a high internal surface area with the strong scattering of light, which results in high light absorption and an excellent full-sun power conversion efficiency of up to 6.4% in a robust, 3 mu m thick dye-sensitized solar cell. | |||||
BibTeX:
@article{Nedelcu2010,
author = {Nedelcu, M. and Guldin, S. and Orilall, M. C. and Lee, J. and Huttner, S. and Crossland, E. J. W. and Warren, S. C. and Ducati, C. and Laity, P. R. and Eder, D. and Wiesner, U. and Steiner, U. and Snaith, H. J.},
title = {Monolithic route to efficient dye-sensitized solar cells employing diblock copolymers for mesoporous TiO2},
journal = {Journal of Materials Chemistry},
year = {2010},
volume = {20},
number = {7},
pages = {1261--1268},
doi = {http://dx.doi.org/10.1039/b920077k}
}
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| Schuettfort, T., Snaith, H.J., Nish, A. & Nicholas, R.J. | Synthesis and spectroscopic characterization of solution processable highly ordered polythiophene-carbon nanotube nanohybrid structures | 2010 | Nanotechnology Vol. 21(2) |
article | DOI |
| Abstract: We report on the synthesis and spectroscopic study of a novel highly ordered nanohybrid structure consisting of a single-walled carbon nanotube (SWNT) coated with highly crystalline regio-regular poly(3-hexylthiophene) (rrP3HT) and discuss the applicability of the nanohybrids in organic photovoltaics. The use of a solvent extraction technique allows the nanohybrids to be produced with a high yield and high purity. We find evidence that the crystallinity of rrP3HT is enhanced in the presence of SWNTs, which introduces a reduced optical band gap and increased carrier mobility in the polymer. Study of the photoluminescence excitation spectra of the SWNTs reveals an efficient energy transfer of excitons created on the rrP3HT to the SWNTs. This energy transfer is expected to limit our ability to use the nanohybrids as a charge separating interface and can therefore explain the low efficiency of P3HT-SWNT solar cells produced to date. In addition, careful consideration of the energy transfer is necessary when attempting to improve state of the art polymer-fullerene photovoltaic devices with SWNTs in order to make use of their high charge carrier mobilities and increased rrP3HT crystallinity. | |||||
BibTeX:
@article{Schuettfort2010,
author = {Schuettfort, T. and Snaith, H. J. and Nish, A. and Nicholas, R. J.},
title = {Synthesis and spectroscopic characterization of solution processable highly ordered polythiophene-carbon nanotube nanohybrid structures},
journal = {Nanotechnology},
year = {2010},
volume = {21},
number = {2},
doi = {http://dx.doi.org/10.1088/0957-4484/21/2/025201}
}
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| Snaith, H.J. | Estimating the Maximum Attainable Efficiency in Dye-Sensitized Solar Cells | 2010 | Advanced Functional Materials Vol. 20(1), pp. 13-19 |
article | DOI |
| Abstract: For an ideal solar cell, a maximum solar-to-electrical power conversion efficiency of just over 30% is achievable by harvesting UV to near IR photons up to 1.1 eV. Dye-sensitized solar cells (DSCs) are, however, not ideal. Here, the electrical and optical losses in the dye-sensitized system are reviewed, and the main losses in potential from the conversion of an absorbed photon at the optical bandgap of the sensitizer to the open-circuit voltage generated by the solar cell are specifically highlighted. In the first instance, the maximum power conversion efficiency attainable as a function of optical bandgap of the sensitizer and the "loss-in-potential" from the optical bandgap to the open-circuit voltage is estimated. For the best performing DSCs with current technology, the loss-in-potential is similar to 0.75eV, which leads to a maximum power-conversion efficiency of 13.4% with an optical bandgap of 1.48 eV (840 nm absorption onset). Mean by which the loss-in-potential could be reduced to 0.4eV are discussed; a maximum efficiency of 20.25% with an optical bandgap of 1.31 eV (940 nm) is possible if this is achieved. | |||||
BibTeX:
@article{Snaith2010,
author = {Snaith, H. J.},
title = {Estimating the Maximum Attainable Efficiency in Dye-Sensitized Solar Cells},
journal = {Advanced Functional Materials},
year = {2010},
volume = {20},
number = {1},
pages = {13--19},
doi = {http://dx.doi.org/10.1002/adfm.200901476}
}
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| Snaith, H.J. & Ducati, C. | SnO2-Based Dye-Sensitized Hybrid Solar Cells Exhibiting Near Unity Absorbed Photon-to-Electron Conversion Efficiency | 2010 | Nano Letters Vol. 10(4), pp. 1259-1265 |
article | DOI |
| Abstract: Improving the solar light harvesting and photon-to-electron conversion efficiency for hybrid, organic inorganic photovoltaics are critical challenges. Titania based solid-state hybrid solar cells are moderately efficient at converting visible photons to electrons, but major electrical losses still remain. A material based paradigm shift is required to dramatically enhance the performance of these devices. Here, we present an investigation into solid-state dye-sensitized solar cells (SDSCs) incorporating a molecular hole-transporter and mesoporous tin oxide electrodes, in place of titania usually employed. We investigate the influence of treating the surface of the SnO2 with different oxides and find that MgO "passivated" SnO2 electrodes demonstrate an unprecedented absorbed photon-to-electron conversion efficiency of near unity across a broad spectral range. A dual surface treatment of TiO2 followed by MgO enables tuning of the solar cell photovoltage, fill factor, and efficiency with visible light absorbing cells delivering 3% solar-to-electrical full sun power conversion efficiency. | |||||
BibTeX:
@article{Snaith2010a,
author = {Snaith, H. J. and Ducati, C.},
title = {SnO2-Based Dye-Sensitized Hybrid Solar Cells Exhibiting Near Unity Absorbed Photon-to-Electron Conversion Efficiency},
journal = {Nano Letters},
year = {2010},
volume = {10},
number = {4},
pages = {1259--1265},
doi = {http://dx.doi.org/10.1021/nl903809r}
}
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| Tiwana, P., Parkinson, P., Johnston, M.B., Snaith, H.J. & Herz, L.M. | Ultrafast Terahertz Conductivity Dynamics in Mesoporous TiO2: Influence of Dye Sensitization and Surface Treatment in Solid-State Dye-Sensitized Solar Cells | 2010 | Journal of Physical Chemistry C Vol. 114(2), pp. 1365-1371 |
article | DOI |
| Abstract: We have used optical-pump terahertz-probe spectroscopy to explore the photoinduced conductivity dynamics in mesoporous anatase TiO2 films, commonly employed as the electron-transporting electrode in dye-sensitized solar cells. We find an intrinsic mobility value of 0.1 cm(2)/(V s) and diffusion length of similar to 20 nm for electron motion through the TiO2 matrix. The photoconductivity dynamics in TiO2 films, both before and after sensitization with a ruthenium bypyridyl complex termed Z907, were examined in order to study the charge injection, trapping, and recombination time scales. We observe a biphasic charge injection from Z907, with a fast sub-500 fs component, followed by a slower 70-200 ps component. This is followed by photoconductivity decay over the first few nanoseconds, predominantly reflecting charge carrier trapping. In addition, we have utilized terahertz spectroscopy to investigate the influence of treating the titania surface with TiCl4 on early-time charge dynamics, In the solar Cells, Surface treatment of the mesoporous TiO2 with TiCl4 is critical to enable efficient operation, Here, we find that neither early-time charge mobility nor charge injection rate or decay times are significantly affected by the treatment, which suggests that it may, instead, have an impact oil phenomena occurring oil longer time scales. | |||||
BibTeX:
@article{Tiwana2010,
author = {Tiwana, P. and Parkinson, P. and Johnston, M. B. and Snaith, H. J. and Herz, L. M.},
title = {Ultrafast Terahertz Conductivity Dynamics in Mesoporous TiO2: Influence of Dye Sensitization and Surface Treatment in Solid-State Dye-Sensitized Solar Cells},
journal = {Journal of Physical Chemistry C},
year = {2010},
volume = {114},
number = {2},
pages = {1365--1371},
doi = {http://dx.doi.org/10.1021/jp908760r}
}
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| Crossland, E.J.W., Nedelcu, M., Ducati, C., Ludwigs, S., Hillmyer, M.A., Steiner, U. & Snaith, H.J. | Block Copolymer Morphologies in Dye-Sensitized Solar Cells: Probing the Photovoltaic Structure-Function Relation | 2009 | Nano Letters Vol. 9(8), pp. 2813-2819 |
article | DOI |
| Abstract: We integrate mesostructured titania arrays into dye-sensitized solar cells by replicating ordered, oriented one-dimensional (1D) columnar and three-dimensional (3D) bicontinuous gyroid block copolymer phases. The solar cell performance, charge transport, and recombination are Investigated. We observe faster charge transport in 1D "wires" than through 3D gyroid arrays. However, owing to their structural instability, the surface area of the wire arrays is low, inhibiting the solar cell performance. The gyroid morphology, on the other hand, outperforms the current state-of-the-art mesoporous nanoparticle films. | |||||
BibTeX:
@article{Crossland2009,
author = {Crossland, E. J. W. and Nedelcu, M. and Ducati, C. and Ludwigs, S. and Hillmyer, M. A. and Steiner, U. and Snaith, H. J.},
title = {Block Copolymer Morphologies in Dye-Sensitized Solar Cells: Probing the Photovoltaic Structure-Function Relation},
journal = {Nano Letters},
year = {2009},
volume = {9},
number = {8},
pages = {2813--2819},
doi = {http://dx.doi.org/10.1021/nl800942c}
}
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| Crossland, E.J.W., Kamperman, M., Nedelcu, M., Ducati, C., Wiesner, U., Smilgies, D.M., Toombes, G.E.S., Hillmyer, M.A., Ludwigs, S., Steiner, U. & Snaith, H.J. | A Bicontinuous Double Gyroid Hybrid Solar Cell | 2009 | Nano Letters Vol. 9(8), pp. 2807-2812 |
article | DOI |
| Abstract: We report the first successful application of an ordered bicontinuous gyroid semiconducting network in a hybrid bulk heterojunction solar cell. The freestanding gyroid network is fabricated by electrochemical deposition into the 10 nm wide voided channels of a self-assembled, selectively degradable block copolymer film. The highly ordered pore structure is ideal for uniform infiltration of an organic hole transporting material, and solid-state dye-sensitized solar cells only 400 nm thick exhibit up to 1.7% power conversion efficiency. This patterning technique can be readily extended to other promising heterojunction systems and is a major step toward realizing the full potential of self-assembly in the next generation of device technologies. | |||||
BibTeX:
@article{Crossland2009a,
author = {Crossland, E. J. W. and Kamperman, M. and Nedelcu, M. and Ducati, C. and Wiesner, U. and Smilgies, D. M. and Toombes, G. E. S. and Hillmyer, M. A. and Ludwigs, S. and Steiner, U. and Snaith, H. J.},
title = {A Bicontinuous Double Gyroid Hybrid Solar Cell},
journal = {Nano Letters},
year = {2009},
volume = {9},
number = {8},
pages = {2807--2812},
doi = {http://dx.doi.org/10.1021/nl803174p}
}
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| Huang, D.M., Snaith, H.J., Gratzel, M., Meerholz, K. & Moule, A.J. | Optical description of solid-state dye-sensitized solar cells. II. Device optical modeling with implications for improving efficiency | 2009 | Journal of Applied Physics Vol. 106(7) |
article | DOI |
| Abstract: We use the optical transfer-matrix method to quantify the spatial distribution of light in solid-state dye-sensitized solar cells (DSCs), employing material optical properties measured experimentally in the accompanying article (Part I) as input into the optical model. By comparing the optical modeling results with experimental photovoltaic action spectra for solid-state DSCs containing either a ruthenium-based dye or an organic indoline-based dye, we show that the internal quantum efficiency (IQE) of the devices for both dyes is around 60% for almost all wavelengths, substantially lower than the almost 100% IQE measured for liquid DSCs, indicating substantial electrical losses in solid-state DSCs that can account for much of the current factor-of-two difference between the efficiencies of liquid and solid-state DSCs. The model calculations also demonstrate significant optical losses due to absorption by 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-OMeTAD) and TiO2 in the blue and to a lesser extent throughout the visible. As a consequence, the more absorptive organic dye, D149, should outperform the standard ruthenium complex sensitizer, Z907, for all device thicknesses, underlining the potential benefits of high extinction coefficient dyes optimized for solid-state DSC operation. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3204985] | |||||
BibTeX:
@article{Huang2009,
author = {Huang, D. M. and Snaith, H. J. and Gratzel, M. and Meerholz, K. and Moule, A. J.},
title = {Optical description of solid-state dye-sensitized solar cells. II. Device optical modeling with implications for improving efficiency},
journal = {Journal of Applied Physics},
year = {2009},
volume = {106},
number = {7},
doi = {http://dx.doi.org/10.1063/1.3204985}
}
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| Moule, A.J., Snaith, H.J., Kaiser, M., Klesper, H., Huang, D.M., Gratzel, M. & Meerholz, K. | Optical description of solid-state dye-sensitized solar cells. I. Measurement of layer optical properties | 2009 | Journal of Applied Physics Vol. 106(7) |
article | DOI |
| Abstract: The efficiency of a photovoltaic device is limited by the portion of solar energy that can be captured. We discuss how to measure the optical properties of the various layers in solid-state dye-sensitized solar cells (SDSC). We use spectroscopic ellipsometry to determine the complex refractive index of each of the various layers in a SDSC. Each of the ellipsometry fits is used to calculate a transmission spectrum that is compared to a measured transmission spectrum. The complexities of pore filling on the fitting of the ellipsometric data are discussed. Scanning electron microscopy and energy dispersive x-ray spectroscopy is shown to be an effective method for determining pore filling in SDSC layers. Accurate effective medium optical constants for each layer are presented and the material limits under which these optical constants can be used are discussed. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3204982] | |||||
BibTeX:
@article{Moule2009,
author = {Moule, A. J. and Snaith, H. J. and Kaiser, M. and Klesper, H. and Huang, D. M. and Gratzel, M. and Meerholz, K.},
title = {Optical description of solid-state dye-sensitized solar cells. I. Measurement of layer optical properties},
journal = {Journal of Applied Physics},
year = {2009},
volume = {106},
number = {7},
doi = {http://dx.doi.org/10.1063/1.3204982}
}
|
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| Nedelcu, M., Lee, J., Crossland, E.J.W., Warren, S.C., Orilall, M.C., Guldin, S., Huttner, S., Ducati, C., Eder, D., Wiesner, U., Steiner, U. & Snaith, H.J. | Block copolymer directed synthesis of mesoporous TiO2 for dye-sensitized solar cells | 2009 | Soft Matter Vol. 5(1), pp. 134-139 |
article | DOI |
| Abstract: The morphology of TiO2 plays an important role in the operation of solid-state dye-sensitized solar cells. By using polyisoprene-block-ethyleneoxide (PI-b-PEO) copolymers as structure directing agents for a sol-gel based synthesis of mesoporous TiO2, we demonstrate a strategy for the detailed control of the semiconductor morphology on the 10 nm length scale. The careful adjustment of polymer molecular weight and titania precursor content is used to systematically vary the material structure and its influence upon solar cell performance is investigated. Furthermore, the use of a partially sp(2) hybridized structure directing polymer enables the crystallization of porous TiO2 networks at high temperatures without pore collapse, improving its performance in solid-state dye-sensitized solar cells. | |||||
BibTeX:
@article{Nedelcu2009,
author = {Nedelcu, M. and Lee, J. and Crossland, E. J. W. and Warren, S. C. and Orilall, M. C. and Guldin, S. and Huttner, S. and Ducati, C. and Eder, D. and Wiesner, U. and Steiner, U. and Snaith, H. J.},
title = {Block copolymer directed synthesis of mesoporous TiO2 for dye-sensitized solar cells},
journal = {Soft Matter},
year = {2009},
volume = {5},
number = {1},
pages = {134--139},
doi = {http://dx.doi.org/10.1039/b815166k}
}
|
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| Plank, N.O.V., Howard, I., Rao, A., Wilson, M.W.B., Ducati, C., Mane, R.S., Bendall, J.S., Louca, R.R.M., Greenham, N.C., Miura, H., Friend, R.H., Snaith, H.J. & Welland, M.E. | Efficient ZnO Nanowire Solid-State Dye-Sensitized Solar Cells Using Organic Dyes and Core-shell Nanostructures | 2009 | Journal of Physical Chemistry C Vol. 113(43), pp. 18515-18522 |
article | DOI |
| Abstract: We have applied a MgO and a ZrO2 shell deposition method to control the interface between two indolene-based organic dyes in solid-state dye-sensitized solar cells. The shell deposition was carried out at less than 100 degrees C, and shell thickness was shown to be 2 nm for the ZrO2 and 6-10 nm for the MgO by transmission electron microscopy. X-ray photoelectron spectroscopy has shown the initial ZnO NWs and core-shell structures have little surface water contamination. The use of suitable dyes, D102 and D149, has led to power conversion efficiency for ZnO NW based hybrid solar cells of 0.71%. Transient absorption measurements indicate that enhancements in photoinduced charge generation with core-shell formation are the main factor leading to the improved device efficiency. | |||||
BibTeX:
@article{Plank2009,
author = {Plank, N. O. V. and Howard, I. and Rao, A. and Wilson, M. W. B. and Ducati, C. and Mane, R. S. and Bendall, J. S. and Louca, R. R. M. and Greenham, N. C. and Miura, H. and Friend, R. H. and Snaith, H. J. and Welland, M. E.},
title = {Efficient ZnO Nanowire Solid-State Dye-Sensitized Solar Cells Using Organic Dyes and Core-shell Nanostructures},
journal = {Journal of Physical Chemistry C},
year = {2009},
volume = {113},
number = {43},
pages = {18515--18522},
doi = {http://dx.doi.org/10.1021/jp904919r}
}
|
|||||
| Snaith, H.J., Petrozza, A., Ito, S., Miura, H. & Gratzel, M. | Charge Generation and Photovoltaic Operation of Solid-State Dye-Sensitized Solar Cells Incorporating a High Extinction Coefficient Indolene-Based Sensitizer | 2009 | Advanced Functional Materials Vol. 19(11), pp. 1810-1818 |
article | DOI |
| Abstract: An investigation of the function of an indolene-based organic dye, termed D149, incorporated in to solid-state dye-sensitized solar cells using 2,2',7,7'- tetrakis(N,N-di-p-methoxypheny-amine)-9,9' - spirobifluorene (spiro-OMeTAD) as the hole transport material is reported. Solar cell performance characteristics are unprecedented. under low light levels, with the solar cells delivering up to 70% incident photon-to-current efficiency (IPCE) and over 6% power conversion efficiency as measured under simulated air mass (AM) 1.5 sun light at 1 and 10 mW cm(-2). However, a considerable nonlinearity. in the photocurrent as intensities approach "full sun" conditions is observed and the devices deliver up to 4.2% power conversion efficiency under simulated sun light of 100 mW cm(-2). The influence of dye-loading upon solar cell operation is investigated and the thin films are probed via photoinduced absorption (PIA) spectroscopy, tune-correlated single-photon counting (TCSPC), and photoluminescence quantum efficiency (PLQE) measurements in order to deduce the cause for the non ideal solar cell performance. The data ! suggest that electron transfer from the photoexcited sensitizer into the TiO2 is only between 10 to 50% efficient and that ionization of the photo excited dye via hole transfer directly to spiro-OMeTAD dominates the charge generation process: A persistent dye bleaching signal is also observed and assigned to a remarkably high density of electrons "trapped" within the dye phase, equivalent to 1.8 x 10(17) cm(-3) under full sun illumination. it is believed that this localized space charge build-up upon the sensitizer is responsible for the non-linearity of photocurrent with intensity and nonoptimum solar. cell performance under full sun conditions. | |||||
BibTeX:
@article{Snaith2009,
author = {Snaith, H. J. and Petrozza, A. and Ito, S. and Miura, H. and Gratzel, M.},
title = {Charge Generation and Photovoltaic Operation of Solid-State Dye-Sensitized Solar Cells Incorporating a High Extinction Coefficient Indolene-Based Sensitizer},
journal = {Advanced Functional Materials},
year = {2009},
volume = {19},
number = {11},
pages = {1810--1818},
doi = {http://dx.doi.org/10.1002/adfm.200801751}
}
|
|||||
| Song, M.H., Kabra, D., Wenger, B., Friend, R.H. & Snaith, H.J. | Optically-Pumped Lasing in Hybrid Organic-Inorganic Light-Emitting Diodes | 2009 | Advanced Functional Materials Vol. 19(13), pp. 2130-2136 |
article | DOI |
| Abstract: Here, the use of metal oxide layers both for charge transport and injection into an emissive semiconducting polymer and also for the control of the in-plane waveguided optical modes in light-emitting diodes (LEDs) is reported. The high refractive index of zinc oxide is used to confine these modes away from the absorbing electrodes, and include a nano-imprinted grating in the polymer layer to introduce distributed feedback and enhance optical out-coupling. These structures show a large increase in the luminescence efficiency over conventional devices, with photoluminescence efficiency increased by up to 45%. Furthermore, optically-pumped lasing in hybrid oxide polymer LEDs is demonstrated. A tuneable lasing emission is also obtained in a single device structure by employing a graduated thickness of a zinc oxide inter-layer. This demonstrates the scope for using such architectures to improve the external efficiency of organic semiconductor LEDs, and opens new possibilities for the realization of polymer injection lasers. | |||||
BibTeX:
@article{Song2009,
author = {Song, M. H. and Kabra, D. and Wenger, B. and Friend, R. H. and Snaith, H. J.},
title = {Optically-Pumped Lasing in Hybrid Organic-Inorganic Light-Emitting Diodes},
journal = {Advanced Functional Materials},
year = {2009},
volume = {19},
number = {13},
pages = {2130--2136},
doi = {http://dx.doi.org/10.1002/adfm.200801833}
}
|
|||||
| Kabra, D., Song, M.H., Wenger, B., Friend, R.H. & Snaith, H.J. | High efficiency composite metal oxide-polymer electroluminescent devices: A morphological and material based investigation | 2008 | Advanced Materials Vol. 20(18), pp. 3447-+ |
article | DOI |
| Abstract: Composite metal-oxide polymer-based electroluminescent diodes are designed to obtain air stable operation along with sub-volt turn on and high brightness. We investigate different structures (mesoporous and compact) and different materials (TiO2 and ZnO) for electron injecting layers, and employ MoO3 for hole injecting layers. The highest efficiencies, close to 3 Cd A(-1), are achieved using compact ZnO. | |||||
BibTeX:
@article{Kabra2008,
author = {Kabra, D. and Song, M. H. and Wenger, B. and Friend, R. H. and Snaith, H. J.},
title = {High efficiency composite metal oxide-polymer electroluminescent devices: A morphological and material based investigation},
journal = {Advanced Materials},
year = {2008},
volume = {20},
number = {18},
pages = {3447--+},
doi = {http://dx.doi.org/10.1002/adma.200800202}
}
|
|||||
| Kuang, D., Klein, C., Snaith, H.J., Humphry-Baker, R., Zakeeruddin, S.M. & Gratzel, M. | A new ion-coordinating ruthenium sensitizer for mesoscopic dye-sensitized solar cells | 2008 | Inorganica Chimica Acta Vol. 361(3), pp. 699-706 |
article | DOI |
| Abstract: A new ion-coordinating ruthenium polypyridyl sensitizer, NaRu(4-carboxylic acid-4'-carboxylate)(4,4'-bis[(triethyleneglycolmethylether) heptylether]-2,2'-bipyridine)(NCS)(2) (coded as K68), has been synthesized and characterized by H-1 NMR, FTIR, UV-Vis absorption and emission spectroscopy. A power conversion efficiency of 6.6% was obtained for dye-sensitized solar cells (DSCs) based on the K68 dye and a newly developed binary ionic liquid electrolyte containing 1-propyl-3-methyl-imidazolium iodide (PMII) and 1-ethyl-3-methyl- imidazolium tetracyanoborate (EMIB(CN)(4)). For a non-volatile organic solvent based electrolyte, a photovoltaic power conversion efficiency of 7.7% was obtained under simulated full sun light and exhibited a good thermal stability during the accelerated test under 80 degrees C in the dark. Solid-state DSCs incorporating K68 also perform remarkably well, out-performing our previously best ruthenium complexes employed in this type of DSC. (c) 2007 Elsevier B.V. All rights reserved. | |||||
BibTeX:
@article{Kuang2008,
author = {Kuang, D. and Klein, C. and Snaith, H. J. and Humphry-Baker, R. and Zakeeruddin, S. M. and Gratzel, M.},
title = {A new ion-coordinating ruthenium sensitizer for mesoscopic dye-sensitized solar cells},
journal = {Inorganica Chimica Acta},
year = {2008},
volume = {361},
number = {3},
pages = {699--706},
doi = {http://dx.doi.org/10.1016/j.ica.2007.05.031}
}
|
|||||
| Petrozza, A., Groves, C. & Snaith, H.J. | Electron transport and recombination in dye-sensitized mesoporous TiO2 probed by photoinduced charge-conductivity modulation spectroscopy with Monte Carlo modeling | 2008 | Journal of the American Chemical Society Vol. 130(39), pp. 12912-12920 |
article | DOI |
| Abstract: We present a combined experimental and theoretical investigation into the charge transport and recombination in dye-sensitized mesoporous TiO2. We electronically probe the photoinduced change in conductivity through in-plane devices while simultaneously optically probing signatures of the charge species. Our quasi-continuous wave technique allows us to build data sets of electron mobility and recombination versus charge density over a wide temperature range. We observe that the charge density dependence of mobility in TiO2 is strong at high temperatures and gradually reduces with reducing temperature, to an extent where at temperatures below 260 K the mobility is almost independent of charge density. The mobility first increases and then decreases with reducing temperature at any given charge density. These observed trends are surprising and consistent with the multiple-trapping model for charge transport only if the trap density-of-states (DoS) is allowed to become less deep and narrower as the temperature reduces. Our recombination measurements and simulations over a broad range of charge density and temperature are also consistent with the above-mentioned varying DoS function when the recombination rate constant is allowed to increase with temperature, itself consistent with a thermally activated charge-transfer process. Further to using the Monte Carlo simulations to model the experimental data, we use the simulations to aid our understanding of the limiting factors to charge transport and recombination. According to our model, we find that the charge recombination is mainly governed by the recombination reaction rate constant and the charge density dependence is mainly a result of the bimolecular nature of the recombination process. The implication to future material design is that if the mobility can be enhanced without increasing the charge density in the film, for instance by reducing the average trap depth, then this will not be at the sacrifice of comparably enhanced recombination and it will greatly increase the charge carrier diffusion lengths in dye-sensitized or mesoscopic solar cells. | |||||
BibTeX:
@article{Petrozza2008,
author = {Petrozza, A. and Groves, C. and Snaith, H. J.},
title = {Electron transport and recombination in dye-sensitized mesoporous TiO2 probed by photoinduced charge-conductivity modulation spectroscopy with Monte Carlo modeling},
journal = {Journal of the American Chemical Society},
year = {2008},
volume = {130},
number = {39},
pages = {12912--12920},
doi = {http://dx.doi.org/10.1021/ja802108r}
}
|
|||||
| Plank, N.O.V., Snaith, H.J., Ducati, C., Bendall, J.S., Schmidt-Mende, L. & Welland, M.E. | A simple low temperature synthesis route for ZnO-MgO core-shell nanowires | 2008 | Nanotechnology Vol. 19(46) |
article | DOI |
| Abstract: We report a hydrothermal synthesis method for MgO shell coatings directly onto the surface of ZnO nanowire arrays. The entire process can be carried out below 100 degrees C. The MgO shells are produced by the addition of 10 mM magnesium nitrate with 0.2 M sodium hydroxide in water, resulting in a shell thickness of up to 8 nm, verified by high resolution transmission electron microscopy. The viability of the MgO layer as a functional element of optoelectronic devices was tested on solid-state organic hole-transporter based dye-sensitized solar cells. Incorporation of the MgO shell into the solar cell resulted in substantive efficiency improvements of over 400% in comparison to the pristine ZnO nanowire based photovoltaics, indicating that electrons can efficiently tunnel through the 'insulating' MgO shell. | |||||
BibTeX:
@article{Plank2008,
author = {Plank, N. O. V. and Snaith, H. J. and Ducati, C. and Bendall, J. S. and Schmidt-Mende, L. and Welland, M. E.},
title = {A simple low temperature synthesis route for ZnO-MgO core-shell nanowires},
journal = {Nanotechnology},
year = {2008},
volume = {19},
number = {46},
doi = {http://dx.doi.org/10.1088/0957-4484/19/46/465603}
}
|
|||||
| Snaith, H.J., Humphry-Baker, R., Chen, P., Cesar, I., Zakeeruddin, S.M. & Gratzel, M. | Charge collection and pore filling in solid-state dye-sensitized solar cells | 2008 | Nanotechnology Vol. 19(42) |
article | DOI |
| Abstract: The solar to electrical power conversion efficiency for dye-sensitized solar cells (DSCs) incorporating a solid-state organic hole-transporter can be over 5%. However, this is for devices significantly thinner than the optical depth of the active composites and by comparison to the liquid electrolyte based DSCs, which exhibit efficiencies in excess of 10%, more than doubling of this efficiency is clearly attainable if all the steps in the photovoltaic process can be optimized. Two issues are currently being addressed by the field. The first aims at enhancing the electron diffusion length by either reducing the charge recombination or enhancing the charge transport rates. This should enable a larger fraction of photogenerated charges to be collected. The second, though less actively investigated, aims to improve the physical composite formation, which in this instance is the infiltration of mesoporous TiO2 with the organic hole-transporter 2,2', 7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Here, we perform a broad experimental study to elucidate the limiting factors to the solar cell performance. We first investigate the charge transport and recombination in the solid-state dye-sensitized solar cell under realistic working conditions via small perturbation photovoltage and photocurrent decay measurements. From these measurements we deduce that the electron diffusion length near short-circuit is as long as 20 mu m. However, at applied biases approaching open-circuit potential under realistic solar conditions, the diffusion length becomes comparable with the film thickness, similar to 2 mu m, illustrating that real losses to open-circuit voltage, fill factor and hence efficiency are occurring due to ineffective charge collection. The long diffusion length near short-circuit, on the other hand, illustrates that another process, separate from ineffective charge collection, is rendering the solar cell less than ideal. We investigate the process of TiO2 mesopore infiltration with spiro-MeOTAD by examining the cross-sectional images of and performing photo-induced absorption spectroscopy on devices with a range of thickness, infiltrated with spiro-MeOTAD with a range of concentrations. We present our interpretation of the mechanism for material infiltration, and by improving the casting conditions demonstrate efficient charge collection through devices of over 7 mu m in thickness. This investigation represents an improvement in our understanding of the limiting factors to the dye-sensitized solar cell. However, much work, focused on composite formation and improved kinetic competition, is required to realize the true potential of this concept. | |||||
BibTeX:
@article{Snaith2008,
author = {Snaith, H. J. and Humphry-Baker, R. and Chen, P. and Cesar, I. and Zakeeruddin, S. M. and Gratzel, M.},
title = {Charge collection and pore filling in solid-state dye-sensitized solar cells},
journal = {Nanotechnology},
year = {2008},
volume = {19},
number = {42},
doi = {http://dx.doi.org/10.1088/0957-4484/19/42/424003}
}
|
|||||
| Snaith, H.J., Karthikeyan, C.S., Petrozza, A., Teuscher, J., Moser, J.E., Nazeeruddin, M.K., Thelakkat, M. & Gratzel, M. | High extinction coefficient "Antenna" dye in solid-state dye-sensitized solar cells: A photophysical and electronic study | 2008 | Journal of Physical Chemistry C Vol. 112(20), pp. 7562-7566 |
article | DOI |
| Abstract: We present a photophysical and device-based investigation of a new bipyridyl-NCS ruthenium complex sensitizer with an extended pi system, in both sensitized TiO2 and incorporated into solid-state dye-sensitized solar cells. We compare this new sensitizer to an analog dye without the extended A system. We observe very similar excited-state absorption spectra and charge recombination kinetics for the two systems. However, the pi-extended senstizer has a phenomenally enhanced molar extinction coefficient which translates into far greater light harvesting and current collection in solid-state dye-sensitized solar cells. We also infer from transient photovoltage measurements that positioning the pendent extended pi system away from the TiO2 surface has induced a favorable dipole shift, generating enhanced open-circuit voltage. The resulting power conversion efficiency for the solar cell has been increased from 2.4% to 3.2% when comparing the new sensitizer to an analogy with no pendent group. | |||||
BibTeX:
@article{Snaith2008a,
author = {Snaith, H. J. and Karthikeyan, C. S. and Petrozza, A. and Teuscher, J. and Moser, J. E. and Nazeeruddin, M. K. and Thelakkat, M. and Gratzel, M.},
title = {High extinction coefficient "Antenna" dye in solid-state dye-sensitized solar cells: A photophysical and electronic study},
journal = {Journal of Physical Chemistry C},
year = {2008},
volume = {112},
number = {20},
pages = {7562--7566},
doi = {http://dx.doi.org/10.1021/jp801714u}
}
|
|||||
| Reddy, P.Y., Giribabu, L., Lyness, C., Snaith, H.J., Vijaykumar, C., Chandrasekharam, M., Lakshmikantam, M., Yum, J.H., Kalyanasundaram, K., Graetzel, M. & Nazeeruddin, M.K. | Efficient Sensitization of nanocrystalline TiO2 films by a near-IR-absorbing unsymmetrical zinc phthalocyanine [BibTeX] |
2007 | Angewandte Chemie-international Edition Vol. 46(3), pp. 373-376 |
article | DOI |
BibTeX:
@article{Reddy2007,
author = {Reddy, P. Y. and Giribabu, L. and Lyness, C. and Snaith, H. J. and Vijaykumar, C. and Chandrasekharam, M. and Lakshmikantam, M. and Yum, J. H. and Kalyanasundaram, K. and Graetzel, M. and Nazeeruddin, M. K.},
title = {Efficient Sensitization of nanocrystalline TiO2 films by a near-IR-absorbing unsymmetrical zinc phthalocyanine},
journal = {Angewandte Chemie-international Edition},
year = {2007},
volume = {46},
number = {3},
pages = {373--376},
doi = {http://dx.doi.org/10.1002/anie.200603098}
}
|
|||||
| Snaith, H.J. & Gratzel, M. | Electron and hole transport through mesoporous TiO2 infiltrated with spiro-MeOTAD | 2007 | Advanced Materials Vol. 19, pp. 3643-+ |
article | DOI |
| Abstract: Charge transport in a solid-state dye-sensitized solar cell is investigated. Unexpectedly, hole transport in the organic component (Spiro-MeOTAD) is faster than the electron transport in the inorganic component (TiO2). The electron mobility or diffusion coefficient through TiO2 does not increase with increasing illumination intensity, as would be predicted by the multitrapping model for electron transport. The results highlight that poor electron transport in TiO2 is a key issue for further improvements in device performance. | |||||
BibTeX:
@article{Snaith2007,
author = {Snaith, H. J. and Gratzel, M.},
title = {Electron and hole transport through mesoporous TiO2 infiltrated with spiro-MeOTAD},
journal = {Advanced Materials},
year = {2007},
volume = {19},
pages = {3643--+},
doi = {http://dx.doi.org/10.1002/adma.200602085}
}
|
|||||
| Snaith, H.J. & Schmidt-Mende, L. | Advances in liquid-electrolyte and solid-state dye-sensitized solar cells | 2007 | Advanced Materials Vol. 19, pp. 3187-3200 |
article | DOI |
| Abstract: This Progress Report highlights recent developments in dye-sensitized solar cells composed of both liquid electrolytes and solid-state hole transport materials. The authors discuss and review the present understanding of and recent developments in the operational processes, such as charge generation, transport, recombination, and E charge collection. Also, the merits and challenges of alternative device approaches are discussed, including extremely thin absorber cells, devices containing inorganic p-type hole-transporters and non-TiO2 mesoporous metal-oxide electrodes employed in dye-sensitized solar cells. | |||||
BibTeX:
@article{Snaith2007a,
author = {Snaith, H. J. and Schmidt-Mende, L.},
title = {Advances in liquid-electrolyte and solid-state dye-sensitized solar cells},
journal = {Advanced Materials},
year = {2007},
volume = {19},
pages = {3187--3200},
doi = {http://dx.doi.org/10.1002/adma.200602903}
}
|
|||||
| Snaith, H.J., Moule, A.J., Klein, C., Meerholz, K., Friend, R.H. & Gratzel, M. | Efficiency enhancements in solid-state hybrid solar cells via reduced charge recombination and increased light capture | 2007 | Nano Letters Vol. 7, pp. 3372-3376 |
article | DOI |
| Abstract: We compare a series of molecular sensitizers in dye-sensitized solar cells containing the organic hole transporter 2,2',7,7'-tetrakis(NN-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Charge recombination is reduced by the presence of "ion-coordinating" moieties on the dye, with the longest electron lifetime and highest solar cell efficiency achieved using a novel sensitizer with diblock alkoxy-alkane pendent groups. By further increasing the optical path length in the active layer, we achieve a power conversion efficiency of over 5% under OF simulated sun light. | |||||
BibTeX:
@article{Snaith2007b,
author = {Snaith, H. J. and Moule, A. J. and Klein, C. and Meerholz, K. and Friend, R. H. and Gratzel, M.},
title = {Efficiency enhancements in solid-state hybrid solar cells via reduced charge recombination and increased light capture},
journal = {Nano Letters},
year = {2007},
volume = {7},
pages = {3372--3376},
doi = {http://dx.doi.org/10.1021/nl071656u}
}
|
|||||
| Snaith, H.J. & Gratzel, M. | Light-enhanced charge mobility in a molecular hole transporter | 2007 | Physical Review Letters Vol. 98(17) |
article | DOI |
| Abstract: We present an investigation into the charge transport through a molecular hole transporter. Under illumination, photoinduced charge transfer occurs from a sensitizer to the hole transporter. The increased hole density results in striking enhancements in film conductivity, up to 10(6), and charge carrier mobility, Up to 10(3). Such enhancements in mobility at low charge densities have not previously been observed in molecular semiconductors, and demonstrate the importance of considering a charge-density dependent mobility in molecular semiconductors employed under photovoltaic operation. | |||||
BibTeX:
@article{Snaith2007c,
author = {Snaith, H. J. and Gratzel, M.},
title = {Light-enhanced charge mobility in a molecular hole transporter},
journal = {Physical Review Letters},
year = {2007},
volume = {98},
number = {17},
doi = {http://dx.doi.org/10.1103/PhysRevLett.98.177402}
}
|
|||||
| Kuang, D.B., Klein, C., Snaith, H.J., Moser, J.E., Humphry-Baker, R., Comte, P., Zakeeruddin, S.M. & Gratzel, M. | Ion coordinating sensitizer for high efficiency mesoscopic dye-sensitized solar cells: Influence of lithium ions on the photovoltaic performance of liquid and solid-state cells | 2006 | Nano Letters Vol. 6(4), pp. 769-773 |
article | DOI |
| Abstract: A Li+ coordinating sensitizer, NaRu(4-carboxylic acid-4'-carboxylate)(4,4'-bis[(triethylene glycol methyl ether) methyl ether]-2,2'-bipyridine)(NCS)(2) (coded as K51), has been synthesized, and the effect of Li+ coordination on its performance in mesoscopic titanium dioxide dye-sensitized solar cells has been investigated. Fourier transform infrared spectra suggest that Li+ coordinates to the triethylene oxide methyl ether side chains on the dye molecules. With the addition of Li+ to a nonvolatile liquid electrolyte, we observe a significant increase in the photocurrent density, with only a small decrease in the open-circuit voltage, contrary to a non ion coordinating dye which displays a large drop in potential with the addition of Li+. For a solar cell incorporating an organic hole-transporter, we find the potential rises with increasing the Li+ concentration in the hole-transporter matrix. For the liquid electrolyte and solid-state cells, we obtain power conversion efficiencies of 7.8% and 3.8%, respectively, under simulated sunlight. | |||||
BibTeX:
@article{Kuang2006,
author = {Kuang, D. B. and Klein, C. and Snaith, H. J. and Moser, J. E. and Humphry-Baker, R. and Comte, P. and Zakeeruddin, S. M. and Gratzel, M.},
title = {Ion coordinating sensitizer for high efficiency mesoscopic dye-sensitized solar cells: Influence of lithium ions on the photovoltaic performance of liquid and solid-state cells},
journal = {Nano Letters},
year = {2006},
volume = {6},
number = {4},
pages = {769--773},
doi = {http://dx.doi.org/10.1021/nl060075m}
}
|
|||||
| Snaith, H.J. & Gratzel, M. | Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells | 2006 | Applied Physics Letters Vol. 89(26) |
article | DOI |
| Abstract: Upon the addition of lithium salts to the hole-transporter matrix, 2,2('),7,7(')-tetrakis(N,N-di-p-methoxypheny-amine)-9,9(')-spirobifluore ne (spiro-MeOTAD), the authors observe a 100-fold increase in conductivity through spiro-MeOTAD within a TiO2 mesoporous network. The authors demonstrate this to be a bulk effect and not due to improved injection at the electrodes. By testing "hole-only" diodes of pure spiro-MeOTAD and those doped with lithium salts, the authors calculate that the hole mobility increases from 1.6x10(-4) to 1.6x10(-3) cm(2)/V s. The authors discuss the possible mechanisms for this significant enhancement in charge mobility and its implication to the dye-sensitized solar cell operation. (c) 2006 American Institute of Physics. | |||||
BibTeX:
@article{Snaith2006,
author = {Snaith, H. J. and Gratzel, M.},
title = {Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells},
journal = {Applied Physics Letters},
year = {2006},
volume = {89},
number = {26},
doi = {http://dx.doi.org/10.1063/1.2424552}
}
|
|||||
| Snaith, H.J., Zakeeruddin, S.M., Wang, Q., Pechy, P. & Gratzel, M. | Dye-sensitized solar cells incorporating a "liquid" hole-transporting material | 2006 | Nano Letters Vol. 6(9), pp. 2000-2003 |
article | DOI |
| Abstract: We present the first application of an amorphous "liquid" organic semiconductor in an optoelectronic device, demonstrating that it is highly suited for use as a hole-transporting material in nanostructured dye-sensitized solar cells. For such devices, we obtain power conversion efficiencies of up to 2.4% under simulated air mass 1.5 solar spectrum at 100 mWcm(-2), and incident photon-to-electron quantum efficiencies in excess of 50%. | |||||
BibTeX:
@article{Snaith2006a,
author = {Snaith, H. J. and Zakeeruddin, S. M. and Wang, Q. and Pechy, P. and Gratzel, M.},
title = {Dye-sensitized solar cells incorporating a "liquid" hole-transporting material},
journal = {Nano Letters},
year = {2006},
volume = {6},
number = {9},
pages = {2000--2003},
doi = {http://dx.doi.org/10.1021/nl061173a}
}
|
|||||
| Snaith, H.J. & Gratzel, M. | The role of a "Schottky barrier" at an electron-collection electrode in solid-state dye-sensitized solar cells | 2006 | Advanced Materials Vol. 18(14), pp. 1910-+ |
article | DOI |
| Abstract: Solid-state dye-sensitized solar cells perform in a strictly different manner when tested under monochromatic as opposed to white-light illumination. Without a UV component in the illumination source, a Schottky barrier is present at the anode interface. Data suggest (see figure) that the generation of surface states, under white-light illumination, results in a pinning of the Fermi level in the TiO2 at the anode interface. Improving this contact facilitates significant improvement in the device performance. | |||||
BibTeX:
@article{Snaith2006b,
author = {Snaith, H. J. and Gratzel, M.},
title = {The role of a "Schottky barrier" at an electron-collection electrode in solid-state dye-sensitized solar cells},
journal = {Advanced Materials},
year = {2006},
volume = {18},
number = {14},
pages = {1910--+},
doi = {http://dx.doi.org/10.1002/adma.200502256}
}
|
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| Snaith, H.J., Schmidt-Mende, L., Gratzel, M. & Chiesa, M. | Light intensity, temperature, and thickness dependence of the open-circuit voltage in solid-state dye-sensitized solar cells | 2006 | Physical Review B Vol. 74(4) |
article | DOI |
| Abstract: We present an analytical and experimental investigation into the origin of the open-circuit voltage in the solid-state dye-sensitized solar cell. Through Kelvin probe microscopy, we demonstrate that a macroscopically uniform electric field exists throughout the nanocomposite between the electrodes. Considering a balance between drift and diffusion currents, and between charge generation and recombination, we develop an analytical expression for the open-circuit voltage which accurately follows experimental data. We find the open-circuit voltage increases with light intensity as 1.7 kT/q, where T is absolute temperature, however it decreases with increasing temperature and device thickness. The intensity dependence arises from the charge generation rate increasing more strongly with intensity than the recombination rate constant, resulting in increased chemical potential within the device. We find that the temperature dependence arises from a reduction in the charge lifetime and not from increased charge diffusion and mobility. The thickness dependence is found to derive from two factors; first, charge recombination sites are distributed throughout the film, enabling more charges to recombine in thicker films before influencing the potential at the electrodes, and second, the average optical power density within the film reduces with increasing film thickness. | |||||
BibTeX:
@article{Snaith2006c,
author = {Snaith, H. J. and Schmidt-Mende, L. and Gratzel, M. and Chiesa, M.},
title = {Light intensity, temperature, and thickness dependence of the open-circuit voltage in solid-state dye-sensitized solar cells},
journal = {Physical Review B},
year = {2006},
volume = {74},
number = {4},
doi = {http://dx.doi.org/10.1103/PhysRevB.74.045306}
}
|
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| Whiting, G.L., Snaith, H.J., Khodabakhsh, S., Andreasen, J.W., Breiby, D., Nielsen, M.M., Greenham, N.C., Friend, P.H. & Huck, W.T.S. | Enhancement of charge-transport characteristics in polymeric films using polymer brushes | 2006 | Nano Letters Vol. 6(3), pp. 573-578 |
article | |
| Abstract: We show that charge-transporting polymer chains in the brush conformation can be synthesized from a variety of substrates of interest, displaying a high degree of stretching and showing up to a 3 orders of magnitude increase in current density normal to the substrate as compared with a spin-coated film. These nanostructured polymeric films may prove to be suitable for electronic devices based on molecular semiconductors as current fabrication techniques often provide little control over film structure. | |||||
BibTeX:
@article{Whiting2006,
author = {Whiting, G. L. and Snaith, H. J. and Khodabakhsh, S. and Andreasen, J. W. and Breiby, D. and Nielsen, M. M. and Greenham, N. C. and Friend, P. H. and Huck, W. T. S.},
title = {Enhancement of charge-transport characteristics in polymeric films using polymer brushes},
journal = {Nano Letters},
year = {2006},
volume = {6},
number = {3},
pages = {573--578}
}
|
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| Snaith, H.J., Zakeeruddin, S.M., Schmidt-Mende, L., Klein, C. & Gratzel, M. | Ion-coordinating sensitizer in solid-state hybrid solar cells [BibTeX] |
2005 | Angewandte Chemie-international Edition Vol. 44(39), pp. 6413-6417 |
article | DOI |
BibTeX:
@article{Snaith2005,
author = {Snaith, H. J. and Zakeeruddin, S. M. and Schmidt-Mende, L. and Klein, C. and Gratzel, M.},
title = {Ion-coordinating sensitizer in solid-state hybrid solar cells},
journal = {Angewandte Chemie-international Edition},
year = {2005},
volume = {44},
number = {39},
pages = {6413--6417},
doi = {http://dx.doi.org/10.1002/anie.200502009}
}
|
|||||
| Snaith, H.J., Kenrick, H., Chiesa, M. & Friend, R.H. | Morphological and electronic consequences of modifications to the polymer anode 'PEDOT : PSS' | 2005 | Polymer Vol. 46(8), pp. 2573-2578 |
article | DOI |
| Abstract: We present a microscopic and electronic investigation of the polymeric anode poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) used as an electrode in photovoltaic and single carrier diodes. PEDOT:PSS is processed from aqueous solution as a colloidal dispersion with excess PSS present. We modify the PEDOT:PSS solution by the addition of a high boiling point alcohol, glycerol, which is known to increase the conductivity of the spin-coated film. Atomic force microscopy indicates swelling and greater aggregation of the PEDOT-rich colloidal particles found in this system. Current voltage characteristics of 'hole-transporting' diodes, formed with gold contacts, suggest less surface enrichment of PSS in the glycerol modified electrode. Through Kelvin probe microscopy, we find the surface potential of glycerol modified PEDOT:PSS decreases by approximately 0.12 eV, which we assign to a reduction in surface enrichment by PSS. Photovoltaic diodes, using a PFB:F8BT polymer blend as the photo-active layer, and glycerol modified PEDOT:PSS anodes are significantly improved as compared to those with unmodified PEDOT:PSS anodes. This is likely to be due to improved hole-injection from the active polymer film into the PEDOT:PSS anode. This emphasises the electronic consequences of the morphological reorientation of the PEDOT and PSS. (c) 2005 Published by Elsevier Ltd. | |||||
BibTeX:
@article{Snaith2005a,
author = {Snaith, H. J. and Kenrick, H. and Chiesa, M. and Friend, R. H.},
title = {Morphological and electronic consequences of modifications to the polymer anode 'PEDOT : PSS'},
journal = {Polymer},
year = {2005},
volume = {46},
number = {8},
pages = {2573--2578},
doi = {http://dx.doi.org/10.1016/j.polymer.2005.01.077}
}
|
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| Snaith, H.J., Whiting, G.L., Sun, B.Q., Greenham, N.C., Huck, W.T.S. & Friend, R.H. | Self-organization of nanocrystals in polymer brushes. Application in heterojunction photovoltaic diodes | 2005 | Nano Letters Vol. 5(9), pp. 1653-1657 |
article | DOI |
| Abstract: We present a new approach to achieving order in molecular semiconductors via alignment of polymer chains using surf ace-initiated polymerization. Polyacrylate brushes grown from transparent conducting electrodes, with triarylamine side groups as hole-transporting components, show characteristics of high mobilities for hole transport. Solution processing a second component with favorable enthalpic interactions can form a composite with mesoscale order and be exploited for heterojunction diodes. We find substantial uptake of CdSe nanocrystals (with diameter in the range 2.5-2.8 nm), and such composites show photovoltaic quantum efficiencies of up to 50%. | |||||
BibTeX:
@article{Snaith2005b,
author = {Snaith, H. J. and Whiting, G. L. and Sun, B. Q. and Greenham, N. C. and Huck, W. T. S. and Friend, R. H.},
title = {Self-organization of nanocrystals in polymer brushes. Application in heterojunction photovoltaic diodes},
journal = {Nano Letters},
year = {2005},
volume = {5},
number = {9},
pages = {1653--1657},
doi = {http://dx.doi.org/10.1021/nl0505039}
}
|
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| Sun, B.Q., Snaith, H.J., Dhoot, A.S., Westenhoff, S. & Greenham, N.C. | Vertically segregated hybrid blends for photovoltaic devices with improved efficiency | 2005 | Journal of Applied Physics Vol. 97(1) |
article | DOI |
| Abstract: Solution-processed photovoltaic devices based on blends of conjugated polymers and inorganic semiconductor tetrapods show high efficiencies due to the good electron transport perpendicular to the plane of the film. Here, we show that by using a high-boiling-point solvent, 1,2,4-trichlorobenzene, instead of chloroform for spin-coating, we can typically obtain a threefold increase in solar power conversion efficiency in devices based on CdSe tetrapods and the poly(p-phenylenvinylene) derivative OC1C10-PPV. The optimized devices show AM1.5 solar power conversion efficiencies of typically 2.1% with some devices as high as 2.8%. The results can be explained by the occurrence of vertical phase separation which leads to an optimal structure for charge collection. Evidence for this structure is obtained by environmental scanning electron microscopy, photocurrent action spectra measurements, time-resolved photoluminescence, and spectroscopic measurements of exciton dissociation and charge-carrier recombination. (C) 2005 American Institute of Physics. | |||||
BibTeX:
@article{Sun2005,
author = {Sun, B. Q. and Snaith, H. J. and Dhoot, A. S. and Westenhoff, S. and Greenham, N. C.},
title = {Vertically segregated hybrid blends for photovoltaic devices with improved efficiency},
journal = {Journal of Applied Physics},
year = {2005},
volume = {97},
number = {1},
doi = {http://dx.doi.org/10.1063/1.1804613}
}
|
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| Snaith, H.J., Greenham, N.C. & Friend, R.H. | The origin of collected charge and open-circuit voltage in blended polyfluorene photovoltaic devices | 2004 | Advanced Materials Vol. 16(18), pp. 1640-+ |
article | DOI |
| Abstract: Polymer blend photovoltaic devices (see Figure) are investigated and the characteristic electron and hole lengths estimated. It is found that for a polymer film exhibiting fine-scale phase separation, only charges generated close to the electrode can be collected. The open-circuit voltage for polymer blend devices is found to be lower than that for bilayer devices, a result of the direct paths from cathode to anode within each blend component. | |||||
BibTeX:
@article{Snaith2004,
author = {Snaith, H. J. and Greenham, N. C. and Friend, R. H.},
title = {The origin of collected charge and open-circuit voltage in blended polyfluorene photovoltaic devices},
journal = {Advanced Materials},
year = {2004},
volume = {16},
number = {18},
pages = {1640--+},
doi = {http://dx.doi.org/10.1002/adma.200305766}
}
|
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| Snaith, H.J. & Friend, R.H. | Morphological dependence of charge generation and transport in blended polyfluorene photovoltaic devices | 2004 | Thin Solid Films Vol. 451, pp. 567-571 |
article | DOI |
| Abstract: We present a compositional analysis of the phase separation, nano-structure and electrical performance of blended hole-accepting and electron-accepting polyfluorene derivatives, in films and in photovoltaic devices. We use varying molecular weights to vary the thin film morphology, without altering the blend composition. We show that photoluminescence quenching is insensitive to variations in the blend morphology but the photovoltaic quantum yield is strongly dependent on morphology. This indicates that charge transport, and not charge generation, is the factor that limits device performance. We develop a model for the charge transport within a meso-scale phase separated film and estimate the distance which charges can travel within the minor component of each phase. (C) 2003 Elsevier B.V. All rights reserved. | |||||
BibTeX:
@article{Snaith2004a,
author = {Snaith, H. J. and Friend, R. H.},
title = {Morphological dependence of charge generation and transport in blended polyfluorene photovoltaic devices},
journal = {Thin Solid Films},
year = {2004},
volume = {451},
pages = {567--571},
doi = {http://dx.doi.org/10.1016/j.tsf.2003.11.046}
}
|
|||||
| Snaith, H.J. & Friend, R.H. | Photovoltaic devices fabricated from an aqueous dispersion of polyfluorene nanoparticles using an electroplating method | 2004 | Synthetic Metals Vol. 147(1-3), pp. 105-109 |
article | DOI |
| Abstract: We report microscopic and device based analysis of thin films of polyfluorene nanoparticles. We use an electroplating technique to form a complete monolayer of polymer nanoparticles on conductive and polymer-coated substrates. We find the electroplated film to be insoluble in organic solvents, and thus are able to build up multilayer structures of electroactive polymers which are originally soluble in common solvents. By spin-coating an F8BT layer from an organic solvent on top of a PFB:F8BT nanoparticle film, we form a multilayer structure. Capping with an aluminium cathode produces a photovoltaic device with substantial performance characteristics. (C) 2004 Elsevier B.V. All rights reserved. | |||||
BibTeX:
@article{Snaith2004b,
author = {Snaith, H. J. and Friend, R. H.},
title = {Photovoltaic devices fabricated from an aqueous dispersion of polyfluorene nanoparticles using an electroplating method},
journal = {Synthetic Metals},
year = {2004},
volume = {147},
number = {1-3},
pages = {105--109},
doi = {http://dx.doi.org/10.1016/j.synthmet.2004.06.054}
}
|
|||||
| Snaith, H.J., Malone, I.B., Ramsdale, C.M., Friend, R.H. & Greenham, N.C. | Charge transport and efficiency in photovoltaic devices based on polyfluorene blends | 2004 | Organic Photovoltaics V Vol. 5520, pp. 26-35 |
article | DOI |
| Abstract: Polymer blends allow control of microstructure in donor-acceptor photovoltaic devices. Here we present measurements of devices containing polyfluorene blend layers of different thicknesses, and we are able to extract characteristic transport lengths for electrons and holes. We also present analytical and numerical modeling of single-layer and bilayer photovoltaic devices, which demonstrates the importance of bound polaron pairs formed after the initial electron transfer from donor to acceptor. Field-assisted dissociation of these polaron pairs is a critical process in determining device performance. | |||||
BibTeX:
@article{Snaith2004c,
author = {Snaith, H. J. and Malone, I. B. and Ramsdale, C. M. and Friend, R. H. and Greenham, N. C.},
title = {Charge transport and efficiency in photovoltaic devices based on polyfluorene blends},
journal = {Organic Photovoltaics V},
year = {2004},
volume = {5520},
pages = {26--35},
doi = {http://dx.doi.org/10.1117/12.559631}
}
|
|||||
| Snaith, H.J., Arias, A.C., Morteani, A.C., Silva, C. & Friend, R.H. | Charge generation kinetics and transport mechanisms in blended polyfluorene photovoltaic devices | 2002 | Nano Letters Vol. 2(12), pp. 1353-1357 |
article | DOI |
| Abstract: We report a compositional analysis of blended hole-accepting and electron-accepting polyfluorene related materials, poly(9,9'-dioctylfluoreneco-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4 -phenylene-diamine) [PFB] and poly(9,9'-dioctylfluorene-co-benzo-thiadiazole) [F8BT], in films and in photovoltaic devices. We find that photoluminescence quenching is insensitive to blend composition but the photovoltaic quantum yield is strongly composition dependent. This indicates that charge transport, and not charge generation, is the factor limiting device performance. We demonstrate that a meso-length scale phase separation optimizes charge transport properties. | |||||
BibTeX:
@article{Snaith2002,
author = {Snaith, H. J. and Arias, A. C. and Morteani, A. C. and Silva, C. and Friend, R. H.},
title = {Charge generation kinetics and transport mechanisms in blended polyfluorene photovoltaic devices},
journal = {Nano Letters},
year = {2002},
volume = {2},
number = {12},
pages = {1353--1357},
doi = {http://dx.doi.org/10.1021/nl0257418}
}
|
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Created by JabRef on 13/03/2011.