High Voc ternary nonfullerene polymer solar cells with improved efficiency and good thermal stability

Abstract

In this work, 2D/1A ternary blend films were designed based on two polymer donors of PTB7-Th and PBDB-T with comparable HOMO levels in combination with a nonfullerene O-IDTBR acceptor, which could display a high open-circuit voltage (Voc) of 1.02 V. With an optimized blend of PTB7-Th:PBDB-T:O-IDTBR = 0.7:0.3:1.5, the ternary polymer solar cells (PSCs) showed PCEs of 11.58%, much higher than 9.74% and 6.99% for PTB7-Th:O-IDTBR and PBDB-T:O-IDTBR binary blend film, respectively. The improved efficiency for the ternary PSCs is due to the obviously elevated short-circuit current density. Higher charge dissociation probabilities, enhanced hole and electron transports, and favorable morphology were found for the ternary blend film. After long thermal annealing at 85 °C for 168 h, a good PCE of 9.37% was still retained by the ternary PSCs, remarkably higher than 5.33–6.27% for the two binary PSCs. In addition, the ternary PSCs with large areas of 0.37, 0.57, and 0.91 cm2 were also evaluated, which displayed PCEs of 10.12%, 9.51%, and 9.01%, respectively. Our results demonstrated a high Voc strategy for ternary PSCs, in which the efficiency and thermal stability could be optimized.