Nonhalogenated‐Solvent‐Processed High‐Performance All‐Polymer Solar Cell with Efficiency over 14%

Rapid developments in material design have led to significant breakthroughs in the power conversion efficiency (PCE) of all‐polymer solar cells (all‐PSCs) in recent years. However, most of these devices are processed using halogenated solvents. Here, nonhalogenated solvent o ‐xylene ( o ‐XY)‐processed all‐PSCs based on PBDB‐T:PJ1 are studied. Interestingly, it is found that the efficiency of the all‐PSCs can be greatly improved to 14.34% by simply increasing the spin‐coating speed during device processing. Careful studies reveal that this improvement could be attributed to the stronger centrifugal force (resulting from a higher spin‐coating speed), shorten the film formation time, and inhibit the excessive aggregation of PJ1. Consequently, a blend film with more reasonable domain size is formed. Based on these findings, another polymer acceptor PJ2, which bears a similar backbone to PJ1 but contains an additional thiophene spacer, is designed. PJ2 exhibits a much weaker aggregation ability and is used as a compatibilizer to improve the miscibility between the PBDB‐T and PJ1. Eventually, PBDB‐T:PJ1:PJ2‐based ternary all‐PSCs with a best PCE of 14.28% but processed under more mild conditions are obtained. These results may provide guidelines for future industrial fabrication of large‐area all‐PSCs.