Fluorine/bromine/selenium multi-heteroatoms substituted dual-asymmetric electron acceptors for o-xylene processed organic solar cells with 19.12% efficiency

Abstract

The development of high-performance near-infrared (NIR) absorbing electron acceptors is a major challenge in achieving high short-circuit current density (JSC) 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 JSC 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 (VOC) of 0.926 V. Inspired by its high VOC 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. 开发高性能的近红外吸收电子受体是实现高短路电流密度并提高有机太阳能电池(OSCs)光电转换效率(PCEs)的重要方法.此工作通过结合双不对称硒稠核和氟、溴杂原子取代端基优势,开发了三种新型多杂原子取代的Y系列受体材料(bi-asy-Y-br、bi-asy-Y-FBr与bi-asyY-FBrF).随着氟化程度的逐渐增加,三种受体的吸收光谱逐步红移.其中, bi-asy-Y-FBrF具有最大的平均静电势分布和最小的分子偶极矩,有利于分子内电荷传输.此外,与D18:bi-asy-Y-Br和D18:bi-asy-Y-FBr共混膜相比, D18:bi-asy-Y-FBrF活性层具有更高的结晶度、更合适的相分离尺度和更低的电荷复合.因此,在二元OSCs中,D18:bi-asy-Y-FBrF器件凭借较高的短路电流密度(26.28mAcm−2),获得了15.74%的PCE值; D18:bi-asy-Y-Br器件凭借优异的开路电压(0.926V),也获得了15.04%的PCE值.受bi-asy-Y-Br开路电压高、与近红外受体BTP-eC9吸收光谱更互补的启发,本文制备了D18:BTP-eC9:bi-asy-Y-Br三元OSCs并获得了19.12%的PCE值,达到目前报道的绿色溶剂加工型OSCs的最高效率范围.