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. Switching the usual direction of electron transport in see-through semiconductors may bring efficiency gains to organic photovoltaics. In n-type dye-sensitized solar cells, transparent indium tin oxide (ITO) is widely used to accept electrons from light-stimulated molecules. By exploiting the seldom-studied electron-donating properties of ITO, Udo Bach from Monash University and co-workers have produced an efficient, p-type organic solar cell. They sintered ITO nanoparticles into thin films and coated them with an aromatic donor-bridge-acceptor dye compound and an iron-based electrolyte. By tweaking the length of a thiophene-based bridge in the dye and applying an appropriate driving voltage, the researchers produced a p-type device that harvested sunlight with an efficiency close to the best n-type dye-sensitized unit. Solar cells where both the anodes and cathodes are photoactive could make low-cost organic devices even more attractive. Indium tin oxide (ITO) is a well-known n-type degenerate semiconductor. Herein, mesoporous ITO is utilized as a photocathode material for p-type dye-sensitized solar cells in place of the commonly applied p-type semiconductors, such as nickel oxide. In conjunction with [Fe(acac)3]0/− as redox mediator and a new sensitizer, an impressive energy conversion efficiency of 1.96±0.12% was achieved. Photoelectron spectroscopy in air revealed that ITO exhibits a significant local density of states arising below −4.8 eV, which enables electron transfer to occur from ITO to the excited dye, giving rise to the sustained photocathodic current.