Photovoltaic Device and Method of Measuring Cumulative Exposure to Light

摘要

This invention concerns a photovoltaic device, and the provision of an apparatus and method for measuring cumulative exposure to visible light. The photovoltaic device according to the invention comprises at least a first electrode layer, a light harvesting layer comprising one or more photoactive compounds capable (individually or together) of forming electron-hole pairs on excitation using light of an appropriate wavelength and an electron-transport material capable of receiving electrons from the excited photoactive compound, and a second electrode layer, and is characterised in that the device further comprises a UV-absorbing layer positioned to intervene in use between the light-harvesting layer and a light source. The function of the UV-absorbing layer is to prevent the excitation of the electron-transporting material and thereby to prevent the bleaching of the light harvesting conducting compound(s). Exposure of the device to light causes reduction of the photovoltaic efficiency over time. The degree of cumulative light exposure is inferred from the photovoltaic efficiency of the device.