Cyano-functionalized organic and polymeric semiconductors for high-performance n-type organic electronic devices

The development of high-performance n-type organic and polymeric semiconductors lags far behind that of p-type counterparts due to a paucity of strongly electron-deficient building blocks. Nevertheless, n-type semiconductors are essential for constructing complementary metal oxide semiconductor (CMOS)-like logic circuits and p-n junction devices. Among various electron-deficient building blocks, cyano-functionalized (hetero)arenes are emerging ones to enable high-performance n-type organic and polymeric semiconductors. In this review, we summarize the recent progress in cyano-functionalized building blocks, including cyano-functionalized indenofluorene, cyano-functionalized imide-based (hetero)arenes, cyano-functionalized benzothiadiazole, and 2-(3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile. Additionally, (hetero)arenes end-capped with dicyanomethylene are also elaborated. Based on these cyano-functionalized building blocks, a great number of n-type organic and polymeric semiconductors are developed, showing much suppressed frontier molecular orbitals (FMOs) compared to their non-cyanated analogues. Thus, very promising device performance in various n-type organic electronic devices, including organic thin-film transistors (OTFTs), organic solar cells (OSCs), and organic thermoelectrics (OTEs), is obtained. These results demonstrate that cyano functionalization is a powerful strategy for developing organic and polymeric semiconductors with deep-lying lowest unoccupied molecular orbitals (LUMOs) for n-type organic electronics. Finally, we offer our insights into the future development of cyano-functionalized n-type organic and polymeric semiconductors.