Highly Efficient All-Polymer Solar Cells Enabled by p-Doping of the Polymer Donor

In this study, we report all-polymer solar cells enabled by a joint effect of p-doping and ternary blend strategies. We apply the p-doping strategy for two material systems based on a new polymer donor named PNDT-T and a conventional polymer PBDB-T. In both cases, the efficiencies are improved significantly upon the p-doping of F4-TCNQ The trace amount of F4-TCNQ contributes to the favorable trap-state filling, charge transfer, and transport but has a weaker effect on optimizing the morphology, leaving room for further improvement. Excitingly, via fabrication of the ternary blend devices based on PNDT-T-0.7:PBDB-T-0.3:DCNBT-IDT0.8 along with p-doping of F4-TCNQ in trace amounts, a significantly improved power conversion efficiency of 11.87% is realized. We find the optimized ternary blend shows high crystallinity, miscibility, and elevated phase separation comparable to those of the binary blend, thus facilitating the improved charge separation and transport.