13.26% Efficiency Polymer Solar Cells by Optimizing Photogenerated Exciton Distribution and Phase Separation with the Third Component

Ternary polymer solar cells (PSCs) are designed by incorporating varied PC₇₁BM into a PBDB-T:INPIC-Si-based binary system. The PC₇₁BM incorporation can replenish weak absorption of PBDB-T and INPIC-Si in the short wavelength from 300 to 500 nm. Effective charge transport channels can be formed in ternary active layers due to good compatibility of the used materials. The optimized ternary PSCs exhibit a power conversion efficiency (PCE) of 13.26% with short-circuit current density (J_SC) of 20.98 mA cm⁻², open-circuit voltage of 0.892 V, and fill factor (FF) of 70.84%. The 13.26% PCE is among the top values for ternary PSCs with fullerene derivative and nonfullerene materials as acceptors. An approximately 12.5% PCE improvement is obtained compared with INPIC-Si-based binary PSCs, originating from simultaneously increased J_SC and FF of the optimized ternary PSCs. The balanced photon harvesting is obtained in the whole wavelength range by regulating PC₇₁BM content in acceptors, leading to increased J_SC of ternary PSCs. The molecular arrangement and phase separation are well optimized in ternary blend films, resulting in the enhanced FF of ternary PSCs. The photogenerated exciton distribution is optimized according to optical field distribution of ternary active layers, which further support the J_SC and FF improvement.