Intensity modulated photocurrent spectroscopy (IMPS) of solid-state polybithiophene-based solar cells

Intensity modulated photocurrent spectroscopy (IMPS) was used to study the mechanism and kinetics of carrier extraction at contacts in polybithiophene-based solid-state photovoltaic cells. The cells were prepared using traditional architecture with ITO/PEDOT and Al contacts. It was shown that such an architecture does not provide a sufficient built-in voltage for the efficient separation of photoexcited carriers without applying considerable external bias. Furthermore, even when such a bias was applied, the resulting dc photocurrents were still very low due to a high rate of recombination at the contacts. The results highlight the importance of improving the efficiency of carrier extraction at contacts and the cell architecture in general if the overall efficiency of polymer-based solar cells is to be further increased.