Conquering the morphology barrier of ternary all-polymer solar cells by designing random terpolymer for constructing efficient binary all-polymer solar cells

The ternary strategy based on two electron donors and one electron acceptor can effectively expand the absorption and photovoltaic performance of all-polymer solar cells (all-PSC). However, it is still challenging to realize the ideal morphology of the ternary blend film through reasonable molecular design. To overcome the morphology barrier of ternary all-PSC, here we replaced physical blending of two donors (P1 and P2) by chemical random ternary copolymerization obtaining a terpolymer namely P1-co-25%P2. The binary all-PSCs constructed by integrating P1-co-25%P2 with a polymerized non-fullerene acceptor PYFT exhibited an impressively high power conversion efficiency (PCE) of 14.67%, which obviously outperformed those of obtained from ternary all-PSCs based on P1:P2:PYFT. Further morphology characterization of these blend films revealed that the incorporation of the P2 unit in the P1 backbone can optimize the 7C-7C stacking, miscibility and phase separation that beneficial to exciton diffusion and charge transport, illustrating the unparalleled superiority of the random ternary copolymerization strategy compared to the ternary blending strategy.

Automated summary

By using the random ternary copolymerization strategy, the morphology barrier of ternary all-polymer solar cells can be overcome, leading to the achievement of a more ideal film morphology and higher photovoltaic conversion efficiency.