Visualizing Macroscopic Inhomogeneities in Perovskite Solar Cells

ACS Energy Letters American Chemical Society (ACS) (2022) 2311-2322

Authors:

Akash Dasgupta, Suhas Mahesh, Pietro Caprioglio, Yen-Hung Lin, Karl-Augustin Zaininger, Robert DJ Oliver, Philippe Holzhey, Suer Zhou, Melissa M McCarthy, Joel A Smith, Maximilian Frenzel, M Greyson Christoforo, James M Ball, Bernard Wenger, Henry J Snaith

Interlayer excitons in MoSe2/2D perovskite hybrid heterostructures - the interplay between charge and energy transfer.

Nanoscale 14:22 (2022) 8085-8095

Authors:

M Karpińska, J Jasiński, R Kempt, JD Ziegler, H Sansom, T Taniguchi, K Watanabe, HJ Snaith, A Surrente, M Dyksik, DK Maude, Ł Kłopotowski, A Chernikov, A Kuc, M Baranowski, P Plochocka

Abstract:

van der Waals crystals have opened a new and exciting chapter in heterostructure research, removing the lattice matching constraint characteristics of epitaxial semiconductors. They provide unprecedented flexibility for heterostructure design. Combining two-dimensional (2D) perovskites with other 2D materials, in particular transition metal dichalcogenides (TMDs), has recently emerged as an intriguing way to design hybrid opto-electronic devices. However, the excitation transfer mechanism between the layers (charge or energy transfer) remains to be elucidated. Here, we investigate PEA2PbI4/MoSe2 and (BA)2PbI4/MoSe2 heterostructures by combining optical spectroscopy and density functional theory (DFT) calculations. We show that band alignment facilitates charge transfer. Namely, holes are transferred from TMDs to 2D perovskites, while the electron transfer is blocked, resulting in the formation of interlayer excitons. Moreover, we show that the energy transfer mechanism can be turned on by an appropriate alignment of the excitonic states, providing a rule of thumb for the deterministic control of the excitation transfer mechanism in TMD/2D-perovskite heterostructures.

Scalable processing for realizing 21.7%-efficient all-perovskite tandem solar modules.

Science (New York, N.Y.) 376:6594 (2022) 762-767

Authors:

Ke Xiao, Yen-Hung Lin, Mei Zhang, Robert DJ Oliver, Xi Wang, Zhou Liu, Xin Luo, Jia Li, Donny Lai, Haowen Luo, Renxing Lin, Jun Xu, Yi Hou, Henry J Snaith, Hairen Tan

Abstract:

Challenges in fabricating all-perovskite tandem solar cells as modules rather than as single-junction configurations include growing high-quality wide-bandgap perovskites and mitigating irreversible degradation caused by halide and metal interdiffusion at the interconnecting contacts. We demonstrate efficient all-perovskite tandem solar modules using scalable fabrication techniques. By systematically tuning the cesium ratio of a methylammonium-free 1.8-electron volt mixed-halide perovskite, we improve the homogeneity of crystallization for blade-coated films over large areas. An electrically conductive conformal "diffusion barrier" is introduced between interconnecting subcells to improve the power conversion efficiency (PCE) and stability of all-perovskite tandem solar modules. Our tandem modules achieve a certified PCE of 21.7% with an aperture area of 20 square centimeters and retain 75% of their initial efficiency after 500 hours of continuous operation under simulated 1-sun illumination.

Solvent-free method for defect reduction and improved performance of p-i-n vapor-deposited perovskite solar cells

ACS Energy Letters American Chemical Society 7 (2022) 1903-1911

Authors:

Kilian Lohmann, Silvia G Motti, Robert DJ Oliver, Alexandra J Ramadan, Harry C Sansom, Qimu Yuan, Karim A Elmestekawy, James M Ball, Laura M Herz, Henry J Snaith, Michael Johnston

Abstract:

As perovskite-based photovoltaics near commercialization, it is imperative to develop industrial-scale defect-passivation techniques. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabricate metal-halide perovskite thin films. We demonstrate markably improved growth and optoelectronic properties for vapor-deposited [CH(NH2)2]0.83Cs0.17PbI3 perovskite solar cells by partially substituting PbI2 for PbCl2 as the inorganic precursor. We find the partial substitution of PbI2 for PbCl2 enhances photoluminescence lifetimes from 5.6 ns to over 100 ns, photoluminescence quantum yields by more than an order of magnitude, and charge-carrier mobility from 46 cm2/(V s) to 56 cm2/(V s). This results in improved solar-cell power conversion efficiency, from 16.4% to 19.3% for the devices employing perovskite films deposited with 20% substitution of PbI2 for PbCl2. Our method presents a scalable, dry, and solvent-free route to reducing nonradiative recombination centers and hence improving the performance of vapor-deposited metal-halide perovskite solar cells.

Optoelectronic properties of mixed iodide-bromide perovskites from first-principles computational modeling and experiment

Journal of Physical Chemistry Letters American Chemical Society 13:18 (2022) 4184-4192

Authors:

Yinan Chen, Silvia G Motti, Robert DJ Oliver, Adam D Wright, Henry J Snaith, Michael B Johnston, Laura M Herz, Marina R Filip

Abstract:

Halogen mixing in lead-halide perovskites is an effective route for tuning the band gap in light emission and multijunction solar cell applications. Here we report the effect of halogen mixing on the optoelectronic properties of lead-halide perovskites from theory and experiment. We applied the virtual crystal approximation within density functional theory, the <i>GW</i> approximation, and the Bethe-Salpeter equation to calculate structural, vibrational, and optoelectronic properties for a series of mixed halide perovskites. We separately perform spectroscopic measurements of these properties and analyze the impact of halogen mixing on quasiparticle band gaps, effective masses, absorption coefficients, charge-carrier mobilities, and exciton binding energies. Our joint theoretical-experimental study demonstrates that iodide-bromide mixed-halide perovskites can be modeled as homovalent alloys, and local structural distortions do not play a significant role for the properties of these mixed species. Our study outlines a general theoretical-experimental framework for future investigations of novel chemically mixed systems.