Realizing efficiency improvement of polymer solar cells by using multi-functional cascade electron transport layers

Contact property between metal oxide electron transport layer (ETL) and active layer is one of the key factors to the performance of polymer solar cells (PSCs). To achieve better lattice matching and fewer defects, indium trioxide (In2O3) and zinc oxide (ZnO) (In2O3/ZnO) were used as the inorganic composite ETL, combining with an organic material PCBM as interface layer to obtain homogeneous phase separation of the active layer. The resulting device demonstrates a high fill factor of 69.83% and power conversion efficiency of 9.036% for PTB7: PC71BM based PSCs. Moreover, the acceptor material of PCBM serving as interface layer can interact with donor material of active layer to promote the exciton dissociation. This study provides a new method to improve the performance of PSCs by using multi-functional cascade electron transport layers.