Acceptor-acceptor type polymers based on cyano-substituted benzochalcogenadiazole and diketopyrrolopyrrole for high-efficiency n-type organic thermoelectrics

The development of n-type organic thermoelectrics (OTEs) falls significantly behind that of their p-type counterparts. Herein, two acceptor-acceptor (A-A) polymers, PDCNBT-DPP and PDCNBSe-DPP, were generated by combining strongly electron-deficient cyano-functionalized benzochalcogenadiazole and diketopyrrolopyrrole building blocks, both of which acted as universal moieties for high-mobility polymers. The A-A polymers showed good solubility, low-lying lowest unoccupied molecular orbital (LUMO) energy levels, and narrow bandgaps; thus, predominant n-type characteristics were achieved in organic thin-film transistors. After n-type doping, both polymers exhibited n-type performance, in which the highest conductivity was 12.36 S cm−1 and a large power factor of 9.22 μW m−1 K−2 was obtained in OTE devices. Our study demonstrated that benzochalcogenadiazole is an excellent building block for developing n-type OTE materials. In addition, the A-A strategy provides an avenue for constructing new types of polymers for high-power n-type OTE materials.