High-performance multiple-donor bulk heterojunction solar cells

Broadening the absorption bandwidth of polymer solar cells by incorporating multiple absorber donors into the bulk-heterojunction active layer is an attractive means of resolving the narrow absorption of organic semiconductors. However, this leads to a much more complicated system, and previous efforts have met with only limited success. Here, several dual-donor and multi-donor bulk-heterojunction polymer solar cells based on a pool of materials with different absorption ranges and preferred molecular structures were studied. The study shows clearly that compatible polymer donors can coexist harmoniously, but the mixing of incompatible polymers can lead to severe molecular disorder and limit device performance. These results provide guidance for the general use of multiple-donor bulk heterojunctions to overcome the absorption limitation and achieve both high performance and fabrication simplicity for organic solar cells.