Prof Henry Snaith FRS

Abstract:

We report the fabrication of light-sensing thin-film transistors based on solution processed films of ZnO, as the channel material, functionalized with an organic dye as the light sensitizer. Due to the presence of the dye, the hybrid devices show exceptionally high photosensitivity to green light of 10 6 and a maximum photoresponsivity on the order of 10 4 A/W. The high performance is argued to be the result of the grain barrier limited nature of electron transport across the polycrystalline ZnO film and its dependence on charge carrier density upon illumination with green light. In addition to the excellent photoresponsivity and signal gain, the hybrid ZnO-dye photoactive layer exhibits high optical transparency. The unique combination of simple device fabrication and distinctive physical characteristics, such as optical transparency, renders the technology attractive for application in large-area transparent photodetectors. © 2012 American Institute of Physics.

Abstract:

Hybrid solar cells based on light absorbing semiconducting polymers infiltrated in nanocrystalline TiO 2 electrodes, have emerged as an attractive concept, combining benefits of both low material and processing costs with well controlled nano-scale morphology. However, after over ten years of research effort, power conversion efficiencies remain around 0.5%. Here, a spectroscopic and device based investigation is presented, which leads to a new optimization route where by functionalization of the TiO 2 surface with a molecular electron acceptor promotes photoinduced electron transfer from a low-band gap polymer(poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4- b0]dithiophene)-alt-4,7-(2,1,3-benzothiadia-zole)] (PCPDTBT) to the metal oxide. This boosts the infrared response and the power conversion efficiency to over 1%. As a further step, by "co-functionalizing" the TiO 2 surface with the electron acceptor and an organic dye-sensitizer, panchromatic spectral photoresponse is achieved in the visible to near-IR region. This novel architecture at the heterojunction opens new material design possibilities and represents an exciting route forward for hybrid photovoltaics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract:

A new self-assembly platform for the fast and straightforward synthesis of bicontinuous, mesoporous TiO 2 films is presented, based on the triblock terpolymer poly(isoprene-b-styrene-b-ethylene oxide). This new materials route allows the co-assembly of the metal oxide as a fully interconnected minority phase, which results in a highly porous photoanode with strong advantages over the state-of-the-art nanoparticle-based photoanodes employed in solid-state dye-sensitized solar cells. Devices fabricated through this triblock terpolymer route exhibit a high availability of sub-bandgap states distributed in a narrow and low enough energy band, which maximizes photoinduced charge generation from a state-of-the-art organic dye, C220. As a consequence, the co-assembled mesoporous metal oxide system outperformed the conventional nanoparticle-based electrodes fabricated and tested under the same conditions, exhibiting solar power-conversion efficiencies of over 5%. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.