Bulk heterojunction based on blends of donor polymers and inorganic acceptor nanoparticles are promising alternatives to all organic solar cells. Although the use of shape tunable semiconductor nanoparticles held great promise for high electron mobility and thus higher device performance, hybrid bulk heterojunction solar cells show nowadays still much lower efficiency than all organic devices. For example blends of poly (3-hexylthiophene ) (P3HT) and zinc oxide (ZnO) nanoparticles have been studied intensively over the last years and only 2 % efficiency has been reported so far, which is still more than twice lower than the performance of those devices made of P3HT:fullerene blends .
In order to further improve device performance, control of blend morphology as well as a deeper understand of the photophysical processes of the hybrid donor-acceptor interface is necessary. An overview over different techniques of morphology control used in hybrid bulk heterojunctions and the corresponding impact on the solar cell performance will be presented. Furthermore alternative mechanisms, which could be involved in the photocurrent generation process of such hybrid solar cells, will be discussed.