Influence of the charge generation profile on the collection efficiency of nanostructured solar cells: a random walk numerical simulation study

The charge collection efficiency (CCE) is a key parameter that determines the overall light-to-energy conversion efficiency of a solar cell. In this study, the influence of the charge generation profile in the active film on the CCE is theoretically analysed. The charge transport process is modelled by random walk numerical simulation in a mesoporous electrode that resembles the morphology of nanostructured metal-oxide electrodes typically used in dye-sensitised solar cells and related optoelectronic devices. Three different charge generation profiles are considered: exponential (Lambert-Beer), Gaussian and combination of both. A power law is found for the dependence of the CCE with respect to the light absorption coefficient in the case of Lambert-Beer profiles. In the case of localised absorptions (Gaussians), the theoretical dependence is found to increase exponentially as the absorption gets closer to the collecting surface.