Cyanothiophene-Flanked Diketopyrrolopyrrole: A New Electron-Deficient Building Block for Unipolar n-Type Polymer Semiconductors

초록

Developing high-performance n-type polymer semiconductors depends on the design and synthesis of strongly electron-deficient units with optimized physicochemical properties. Here, we report a novel diketopyrrolopyrrole derivative (CTDPP) by integrating electron-withdrawing cyano groups into the benchmark thiophene-flanked DPP (TDPP). The new CTDPP not only preserves the high backbone coplanarity of its parent structure, but also exhibits the deepest lowest unoccupied molecular orbital energy level among all DPP derivatives reported and a notably short pi-pi stacking distance (similar to 3.36 & Aring;) in the single-crystal structure, rendering it an excellent building block for constructing high-performance n-type polymers. When incorporated into polymer backbones, the CTDPP-based polymers show unipolar n-type transport characteristics, with a maximum field-effect electron mobility exceeding 0.1 cm2 V-1 s-1 and excellent n-type dopability even at low dopant loadings. Consequently, the polymers achieve remarkable n-type thermoelectric performance with a maximum electrical conductivity of 28.8 S cm-1 and power factor of 34.11 mu W m-1 K-2, thus leading to the highest figure-of-merit (ZT) of 0.08, which is among the highest values for unipolar n-type polymers. These results highlight the effectiveness of CTDPP as a versatile highly electron-deficient building block for high-performance n-type polymers and offer novel design principles for the development of DPP-based materials in organic electronics.

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