15.4% Efficiency all-polymer solar cells

We report all-polymer solar cells (All-PSCs) with record-high power conversion efficiency (PCE) through tuning the molecular weights of the polymer donor (PBDB-T) to form optimal active layer morphology. By combining the polymer donors with a newly reported polymer acceptor (PJ1), an unprecedented high PCE of 15.4% and fill factor over 75% were achieved for the All-PSCs with the medium molecular weight polymer donor (PBDB-TMW), which is the highest value for All-PSCs reported so far. Detailed morphology investigation revealed that the proper phase separation in the PBDB-TMW:PJ1 blend should account for the superior device performance as PBDB-TMW exhibits appropriate miscibility with the polymer acceptor PJ1. These results demonstrated that the device performance of All-PSCs could be fully comparable to that of small molecular acceptor-based PSCs. The formation of optimized morphology via precise control of molecular weights of polymer donors and acceptors is crucial to achieve this goal.