Anomalous photocurrent response of hybrid TiO2:P3HT solar cells under different incident light wavelengths

Abstract

Ordered mesoporous titania present optimum optical and electronic characteristics for solar cells applications. Hybrid solar cells that combine a dye polymer and porous titania is being studied as an inexpensive alternative to solid state photoconversion devices and the role of the inorganic/organic interface is relevant to understanding the efficiency parameters. Many reports have described UV enhancement and light soaking effects for solid state hybrid cells containing titania. In this work, we study devices fabricated by incorporating P3HT into the ordered pores of a sol-gel synthesized nanocrystalline titania. We observe that the spectral response is modified upon illumination at different wavelengths. When irradiated with UV light (below 370 nm), the spectral response is drastically enhanced but when shined with visible light, the external quantum efficiency is reduced. Both effects are reversible such that several enhancement/degradation cycles can be performed. The detrimental visible light effect takes longer than the UV enhancement, which suggests a polymer mediated mechanism. Upon AM 1.5 illumination, both opposing effects are present and results in a Jsc that is sensitive to the measuring time and the test irradiation spectrum.