A High‐Mobility n‐Type Noncovalently‐Fused‐Ring Polymer for High‐Performance Organic Thermoelectrics
Tao Shen, Di Liu, Jianqi Zhang, Zhixiang Wei, Yang Wang
Abstract
Abstract Conjugated polymers are emerging as competitive candidates for organic thermoelectrics (OTEs). However, to make the device truly pervasive, both p‐ and n‐type conjugated polymers are essential. Despite great efforts, no n‐type equivalents to the p‐type benchmark PEDOT:PSS exist to date mainly due to the low electrical conductivity (σ). Herein, a near‐amorphous n‐type conjugated polymer, namely pDFSe, is reported with high σ by achieving the synergy between charge transport and doping efficiency. The polymer pDFSe is synthesized based on an acceptor‐triad moiety of diketopyrrolopyrrole‐difluorobenzoselenadiazole‐diketopyrrolopyrrole (DFSe), which has the noncovalently‐fused‐ring structure to reinforce the backbone rigidity. Furthermore, an axisymmetric thiophene‐selenophene‐thiophene donor is introduced, which enables the formation of near‐amorphous microstructures. The above merits ensure good doping efficiency without scarifying efficient intrachain charge‐carrier transport. Thus, pDFSe‐based n‐type transistors exhibit high electron mobility up to 6.15 cm 2 V −1 s −1 , much higher than its reference polymer pDSe without the noncovalently‐fused‐ring structure (0.77 cm 2 V −1 s −1 ). Further upon n‐doping, pDFSe demonstrates excellent σ of 62.6 S cm −1 and maximum power factor of 133.1 μW m −1 K −2 , which are among the highest values reported for solution‐processed n‐type polymers. The results demonstrate the great potential of near‐amorphous n‐type conjugated polymers with noncovalently‐fused‐ring structure for the next‐generation OTEs.