Thiazole Imide-Based All-Acceptor Homopolymer: Achieving High-Performance Unipolar Electron Transport in Organic Thin-Film Transistors

Abstract

High-performance unipolar n-type polymer semiconductors are critical for advancing the field of organic electronics, which relies on the design and synthesis of new electron-deficient building blocks with good solubilizing capability, favorable geometry, and optimized electrical properties. Herein, two novel imide-functionalized thiazoles, 5,5′-bithiazole-4,4′-dicarboxyimide (BTzI) and 2,2′-bithiazolothienyl-4,4′,10,10′-tetracarboxydiimide (DTzTI), are successfully synthesized. Single crystal analysis and physicochemical study reveal that DTzTI is an excellent building block for constructing all-acceptor homopolymers, and the resulting polymer poly(2,2′-bithiazolothienyl-4,4′,10,10′-tetracarboxydiimide) (PDTzTI) exhibits unipolar n-type transport with a remarkable electron mobility (μ_e) of 1.61 cm² V⁻¹ s⁻¹, low off-currents (I_off) of 10⁻¹⁰−10⁻¹¹ A, and substantial current on/off ratios (I_on/I_off) of 10⁷−10⁸ in organic thin-film transistors. The all-acceptor homopolymer shows distinctive advantages over prevailing n-type donor−acceptor copolymers, which suffer from ambipolar transport with high I_offs > 10⁻⁸ A and small I_on/I_offs < 10⁵. The results demonstrate that the all-acceptor approach is superior to the donor−acceptor one, which results in unipolar electron transport with more ideal transistor performance characteristics.

Electron-deficient thiazole imides are synthesized, which enables development of all-acceptor homopolymers. The polymer PDTzTI exhibits a remarkable electron mobility of 1.61 cm² V⁻¹ s⁻¹ with minimal off-currents of 10⁻¹⁰−10⁻¹¹ A and substantial current on/off ratios of 10⁷−10⁸ in the saturation regime, thus showing distinctive advantages over traditional donor−acceptor copolymers, which suffer from high off-currents and small on/off ratios.

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