High-Efficiency Ternary Polymer Solar Cells Based on Intense FRET Energy Transfer Process

A new wide band gap polymer PBDTPS-FTAZ is designed and synthesized to form complementary absorption with non-fullerene acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone)-5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d':2,3'-d']-s-indaceno[1,2-b:5,6-b'] dithiophene (ITIC). The optimized device utilizing PBDTPS-FTAZ:ITIC as active layer exhibits a power conversion efficiency (PCE) of 8.53%. The external quantum efficiency (EQE) spectrum indicates that the binary-blend device suffers relatively low photo response in the 450-550nm region. Therefore, the fullerene derivative PC71BM and a wide band gap donor polymer P(p-FDBND-2T) with the absorption region of 450-550nm are added to the PBDTPS-FTAZ:ITIC system to construct ternary blend solar cell, respectively. As a result, ternary-blend solar cells based on two configurations (D:A(1):A(2) and D-1:D-2:A) both deliver high PCE over 10% using the conventional device structure. Interestingly, the D-1:D-2:A type ternary solar cell exhibits a higher open circuit voltage (V-OC) along with an intense energy transfer process regardless of the undesirable energy level alignment and reached a high PCE of 11.46%.