Influence of an Inorganic Interlayer on Exciton Separation in Hybrid Solar Cells

[Image: see text] It has been shown that in hybrid polymer–inorganic photovoltaic devices not all the photogenerated excitons dissociate at the interface immediately, but can instead exist temporarily as bound charge pairs (BCPs). Many of these BCPs do not contribute to the photocurrent, as their long lifetime as a bound species promotes various charge carrier recombination channels. Fast and efficient dissociation of BCPs is therefore considered a key challenge in improving the performance of polymer–inorganic cells. Here we investigate the influence of an inorganic energy cascading Nb(2)O(5) interlayer on the charge carrier recombination channels in poly(3-hexylthiophene-2,5-diyl) (P3HT)–TiO(2) and PbSe colloidal quantum dot–TiO(2) photovoltaic devices. We demonstrate that the additional Nb(2)O(5) film leads to a suppression of BCP formation at the heterojunction of the P3HT cells and also a reduction in the nongeminate recombination mechanisms in both types of cells. Furthermore, we provide evidence that the reduction in nongeminate recombination in the P3HT–TiO(2) devices is due in part to the passivation of deep midgap trap states in the TiO(2), which prevents trap-assisted Shockley–Read–Hall recombination. Consequently a significant increase in both the open-circuit voltage and the short-circuit current was achieved, in particular for P3HT-based solar cells, where the power conversion efficiency increased by 39%.