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

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 (<b>CTDPP</b>) by integrating electron-withdrawing cyano groups into the benchmark thiophene-flanked DPP (<b>TDPP</b>). The new <b>CTDPP</b> 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 π–π stacking distance (∼3.36 Å) in the single-crystal structure, rendering it an excellent building block for constructing high-performance n-type polymers. When incorporated into polymer backbones, the <b>CTDPP</b>-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 μW m^–1 K^–2, thus leading to the highest figure-of-merit (<i>ZT</i>) of 0.08, which is among the highest values for unipolar n-type polymers. These results highlight the effectiveness of <b>CTDPP</b> 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.