Slow charge recombination at a dye sensitized nanocrystalline TiO_2/ organic semiconductor heterojunction employing A1_2O_3 coatings

摘要

Control of charge interfacial charge transfer is central to the design of photovoltaic devices. We report herein the application of insulating metal oxide blocking layers to control the charge recombination kinetics at a solid-state dye sensitised nanocrystalline inorganic / organic semiconductor interface. We show that the conformal growth of a ～ 1 nm thick overlayer of Al_2O_3 on a preformed nanocrystalline TiO_2 film results in a ～3-fold retardation in the rate of charge recombination at such an interface. This observation shows a good correlation with the current/voltage characteristics of dye sensitised nanocrystalline solar cells fabricated from such films, with the Al_2O_3 coating resulting in a 40 % improvement in overall device efficiency.