Indium tin oxide as a semiconductor material in efficient p-type dye-sensitized solar cells

Indium tin oxide (ITO) is a well-known n-type degenerate semiconductor with a wide variety of electronic and optoelectronic applications. Herein ITO is utilized as a photocathode material in p-type dye-sensitized solar cells in place of the commonly applied and highly colored nickel oxide (NiO) semiconductor. The application of mesoporous ITO photocathodes, [Fe(acac)3] 0/ - as a redox mediator and a new organic dye afforded an impressive energy conversion efficiency of 1.96 ± 0.12%. Comparative transient absorption spectroscopic studies indicated that the recombination rate at the ITO-electrolyte interface is two orders of magnitude faster than that of NiO. Analysis of the operation mechanism of the ITO-based devices with ultraviolet photon spectroscopy and photoelectron spectroscopy in air showed that ITO exhibits a significant local density of states arising below - 4.8 eV, which enables electron transfer to occur from the ITO to the excited dye, thus giving rise to the sustained photocathodic current.