Charge transport dynamics of a C6H4NH2CuBr2I/TiO2 heterojunction in aqueous solution under reverse bias.

The photocurrent output of the C6H4NH2CuBr2I/TiO2 heterojunction photoelectrode in an aqueous solution is super stable even after 30 000 s. However, the photocurrent is extremely weak. Intensity-modulated photocurrent spectroscopy revealed that the electron transfer in the C6H4NH2CuBr2I/TiO2 photoelectrode without bias is not sufficiently fast to compete with the charge recombination process due to the short diffusion length (∼23 nm), resulting in a low photocurrent. The charge separation and charge transfer efficiency in the bulk of C6H4NH2CuBr2I could be significantly improved under a small reverse electric field (Er), resulting in an enhanced photocurrent.