Revisiting Indolo[3,2‐b]carbazole: Synthesis, Structures, Properties, and Applications

Indolo[3,2‐b]carbazole presents a π‐skeleton with a remarkable electronic structure and interesting potential applications. It is, however, also associated with ambiguity and controversy. Herein, new derivatives of indolo[3,2‐b]carbazole are reported and they have enabled a comprehensive study on the electronic structure of indolo[3,2‐b]carbazole and the development of a new n‐type organic semiconductor. Experimental and computational studies show that indolo[3,2‐b]carbazole has a largely localized p‐benzoquinonediimine moiety and significant antiaromaticity. When substituted with (4‐silylethynyl)phenyl groups, the indolo[3,2‐b]carbazole exhibits one‐dimensional π–π stacking and functions as an n‐type organic semiconductor in solution‐processed field effect transistors. The syntheses of new derivatives of indolo[3,2‐b]carbazole have enabled a comprehensive study on the remarkable electronic structure of indolo[3,2‐b]carbazole. This work has also led to the development of a new n‐type organic semiconductor for solution‐processed organic field effect transistors.