High efficiency ternary organic solar cells based on two nonfused ring electron acceptors with similar molecular structure

Abstract

Organic solar cells (OSCs) based on nonfused ring electron acceptors (NFREAs) have shown great potential for future commercial applications due to their reduced synthesis complexity and low cost, and ternary strategy is a promising path for further boosting the development of NFREAs-based OSCs. Herein, two NFREAs FO-4Cl and FO-N with similar molecular structure are employed to fabricate high-performance ternary OSCs via combining a commonly used polymer donor PBDB-T. The PBDB-T:FO-4Cl and PBDB-T:FO-N binary devices can exhibit PCEs of 12.05% and 11.33%, respectively. Incorporating FO-N into the binary blend PBDB-T:FO-4Cl, the PBDB-T:FO-4Cl:FO-N ternary device can achieve a significantly improved PCE of 13.15% with a Voc of 0.87 V, a Jsc of 20.59 mA/cm2 and an FF of 73.02%, which is 9% and 16% higher than the PBDB-T:FO-4Cl and PBDB-T:FO-N based binary devices, respectively. The enhanced Jsc and FF can be ascribed to the enhanced photon harvesting, improved film morphology and high and balanced charge transport. Meanwhile, the Voc of ternary devices are gradually improved after the introduction of the high-lying LUMO component FO-N, which demonstrates that the two acceptors may form alloy state in the blend system. Our results demonstrate that ternary strategy is an effective path for further boosting the performance of NFREA-based OSCs by incorporating isogenous acceptors.