Huge suppression of charge recombination in P3HT-ZnO organic-inorganic hybrid solar cells by locating dyes at the ZnO/P3HT interfaces.

The charge separation and charge recombination dynamics in P3HT-ZnO and P3HT-dye-ZnO bulk heterojunction organic-inorganic hybrid solar cells (OIHSCs) prepared by a one-pot method were studied using a transient absorption (TA) method, both for optical absorption of P3HT in the visible region and for optical absorption of SQ36 in the NIR region. In the case of P3HT-ZnO, the charge separation was very fast, occurring within 1 ps. On the other hand, high charge recombination between electrons in the surface states and/or the conduction band of ZnO and holes in P3HT was observed. In the case of P3HT-dye-ZnO, we found that the charge recombination could be greatly suppressed by locating the dye at the P3HT/ZnO interfaces while maintaining a fast charge separation rate (a few ps to 10 ps). Our findings provide one methodology for the design of OIHSCs for improving their conversion efficiency, which is to position the dye at the appropriate BHJ interfaces.