Skeletal Formation of Carbocycles with CO2: Selective Synthesis of Indolo[3,2-b]carbazoles or Cyclophanes from Indoles, CO2, and Phenylsilane

The catalytic reactions of indoles with CO2 and phenylsilane afforded indolo[3,2-b]carbazoles, where the fused benzene ring was constructed by forming two C-H bonds and four C-C bonds with two CO2 molecules via deoxygenative conversions. Nine-membered cyclophanes made up of three indoles and three CO2 molecules were also obtained, where the cyclophane framework was constructed by forming six C-H bonds and six C-C bonds. These multicomponent cascade reactions giving completely different carbocycles were switched simply by choosing the solvent, acetonitrile or ethyl acetate.

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

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.