Synthesis of 3H‐Benzo[e]indoline and Its Application to Small‐Molecule Organic Solar Cells

A squaraine‐based small molecule (USQ‐BI) bearing 3H‐benzo[e]indoline was synthesized as an electron donor, and the corresponding organic solar cells show power conversion efficiency of 5.35 % with an excellent short circuit current of over 15 mA cm−2. The hole mobility of USQ‐BI was about 5 times (9.57×10−5 vs. 2.00×10−5 cm2 V−1 s−1) higher than that of indoline‐based squaraine. Make and apply: A new indoline derivative, 3H‐benzo[e]indoline, was synthesized through Fischer indole synthesis, and its application to small‐molecule photovoltaics has been explored with a promising short circuit current of over 15 mA cm−2.