Aspects of the photoelectrochemistry of nanocrystalline systems

The properties of nanocrystalline electrodes are reviewed with particular e mphasis on electron transport in dye-sensitised nanocrystalline photovoltai c cells. Solutions of the electron generation/collection problem are presen ted for steady-state, transient and periodic illumination. The influence of illumination geometry, absorption coefficient, electron diffusion coeffici ent, electron lifetime, electron trapping and electron extraction kinetics are discussed. The experimental methods used to study nanocrystalline photo electrodes are reviewed. Experimental results obtained in studies of high p erformance dye-sensitised TiO2 photovoltaic cells by intensity modulated ph otocurrent and photovoltage spectroscopy are analysed using analytical expr essions derived by solution of the generation/collection problem. The measu red values of electron diffusion coefficient and electron lifetime are disc ussed and related to the design criteria for high efficiency nanocrystallin e photovoltaic cells. The possibility of detecting photoinjected electrons by intensity modulated near IR transmittance measurements is demonstrated. (C) 1999 Elsevier Science Ltd. All rights reserved.