Electron transport in solid-state dye-sensitized solar cells based on polyaniline

Solid-state dye-sensitized solar cells (DSCs) were prepared using polaniline (PANI) as hole-transport material. The charge transport and recombination in the cells were studied by means of intensity modulated photocurrent spectroscopy (IMPS) and intensity modulated photovoltage spectroscopy ( IMVS). On the basis of lifetime ( tau (n)) and mean transit time (tau (d)) of the electrons in nanoporous TiO2 film and fitting of the IMPS response, the effective diffusion coefficient ( D (n)) and the diffusion length ( L (n)) of electrons in the TiO2 film were acquired. The electron lifetime in the PANI-based DSCs was about 10 times lower than their liquid counterparts, indicating a much more serious recombination of photogenerated electrons in the TiO2 film, very likely mainly with holes of oxidized dye molecules. With increase in the thickness of TiO2 film, both tau (n) and tau (d) decreased, whereas L-n and D-n increased; and the better performance of the solid-state cells was available only in a suitable thickness range TiO2 films.