Detection of inhomogeneous dye distribution in dye sensitised nanocrystalline solar cells by intensity modulated photocurrent spectroscopy (IMPS)

The transport of photoinjected electrons in dye sensitised nanocrystalline TiO2 photovoltaic cells has been studied by intensity modulated photocurren t spectroscopy (IMPS). The existence of a dye-free TiO2 region adjacent to the substrate contact in some cells has been inferred from the characterist ic shape of the IMPS response associated with delayed transport of photoinj ected electrons across the dye-free region. The delay is absent in the case of cells with uniform dye distribution. The IMPS response of a cell with i nhomogeneous dye loading was fitted using a simple two-layer model to descr ibe the dye distribution. The results indicate that IMPS is a useful diagno stic tool to detect inhomogeneous dye distributions in nanocrystalline sola r cells. (C) 1999 Elsevier Science S.A. All rights reserved.