Fluorine/bromine/selenium multi-heteroatoms substituted dual-asymmetric electron acceptors for o-xylene processed organic solar cells with 19.12% efficiency
Yibo Zhou, Guangyu Qi, Han Liu, Hairui Bai, Tengfei Li, Muhammad Hamza Maqsood, Chang Liu, Bohao Song, Na Chen, Guanghao Lu, Chao Gao, Yuhang Liu, Wenyan Su, Huiling Du, Ruijie Ma, Wei Ma, Qunping Fan
Abstract
Abstract The development of high-performance near-infrared (NIR) absorbing electron acceptors is a major challenge in achieving high short-circuit current density ( J SC ) to increase power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, three new multi-heteroatomized Y-series acceptors (bi-asy-Y-Br, bi-asy-Y-FBr, and bi-asy-Y-FBrF) were developed by combining dual-asymmetric selenium-fused core and brominated end-groups with different numbers of fluorine substitutions. With gradually increasing fluorination, three acceptors exhibit red-shift absorption. Among them, bi-asy-Y-FBrF presents planar molecular geometry, the maximum average electrostatic potential, and the minimum molecular dipole moment, which are conducive to intramolecular packing and charge transport. Moreover, D18:bi-asy-Y-FBrF active layer presents higher crystallinity, more suitable phase separation, and reduced charge recombination compared to D18:bi-asy-Y-Br and D18:bi-asy-Y-FBr blends. Consequently, among theses binary OSCs, D18:bi-asy-Y-FBrF device achieves a higher PCE of 15.74% with an enhanced J SC of 26.28 mA cm −2 , while D18:bi-asy-Y-Br device obtains a moderate PCE of 15.04% with the highest open-circuit voltage ( V OC ) of 0.926 V. Inspired by its high V OC and complementary absorption with NIR-absorbing BTP-eC9 as acceptor, bi-asy-Y-Br is introduced into binary D18:BTP-eC9 to construct ternary OSCs, achieving a further boosted PCE of 19.12%, which is among the top values for the reported green solvent processed OSCs.