ИСТИНА

In this work, we performed detailed analysis of the mechanism of non-geminate recombination in P3HT/PCBM bulk heterojunction organic solar cells. We found that the high rate of non-geminate recombination can be attributed to the formation of a large density of interfacial states at the P3HT/PCBM interface inside the device. These states are not involved in carrier extraction and act as recombination centers only. Furthermore, the occurrence of these states is found to be directly related to exposure of the cells to atmospheric contaminants. Exclusion of atmospheric exposure through encapsulation was effective in eliminating interfacial recombination, whereas devices that were not encapsulated demonstrated a significant amount of interfacial recombination that was dependent on the photoactive layer composition. Our results suggest that IMPS can be used as a diagnostic tool to predict the performance of bulk heterojunction organic solar cells.