Benzotriazole‐Based 3D Four‐Arm Small Molecules Enable 19.1 % Efficiency for PM6 : Y6‐Based Ternary Organic Solar Cells

• Published in: Angewandte Chemie International Edition 2023-09, Vol.62 (39), p.e202306847-n/a
• Main Authors: Li, Xiangyu, Tang, Ailing, Wang, Helin, Wang, Zongtao, Du, Mengzhen, Guo, Qiang, Guo, Qing, Zhou, Erjun
• Format: Article
• Language: English
• Subjects: 3D Configurations; Alloys; Benzotriazole; Charge transfer; Charge transport; Energy charge; Energy loss; Energy Transfer; Molecular energy levels; Molecular structure; Multi-Arm Small-Molecule Acceptors; Photovoltaic cells; Photovoltaics; Solar cells; Ternary Organic Solar Cells
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202306847

A third component featuring a planar backbone structure similar to the binary host molecule has been the preferred ingredient for improving the photovoltaic performance of ternary organic solar cells (OSCs). In this work, we explored a new avenue that introduces 3D‐structured molecules as guest acceptors. Spirobifluorene (SF) is chosen as the core to combine with three different terminal‐modified (rhodanine, thiazolidinedione, and dicyano‐substituted rhodanine) benzotriazole (BTA) units, affording three four‐arm molecules, SF‐BTA1, SF‐BTA2, and SF‐BTA3, respectively. After adding these three materials to the classical system PM6 : Y6, the resulting ternary devices obtained ultra‐high power‐conversion efficiencies (PCEs) of 19.1 %, 18.7 %, and 18.8 %, respectively, compared with the binary OSCs (PCE=17.4 %). SF‐BTA1‐3 can work as energy donors to increase charge generation via energy transfer. In addition, the charge transfer between PM6 and SF‐BTA1‐3 also acts to enhance charge generation. Introducing SF‐BTA1‐3 could form acceptor alloys to modify the molecular energy level and inhibit the self‐aggregation of Y6, thereby reducing energy loss and balancing charge transport. Our success in 3D multi‐arm materials as the third component shows good universality and brings a new perspective. The further functional development of multi‐arm materials could make OSCs more stable and efficient. We synthesized three 3D four‐arm small molecules with spirobifluorene as the central core and different end‐group‐modified benzotriazole units as arms. By incorporating four‐arm molecules, PM6 : Y6‐based ternary organic solar cells (OSCs) achieved improved efficiencies of 18.7–19.1 %, benefiting from triggered multiple mechanisms and the inhibited excessive aggregation of Y6. Our results open a new avenue for the design of promising guest molecules for ternary OSCs.