(3Z,3′Z)-3,3′-(Hydrazine-1,2-diylidene)bis(indolin-2-one) as a new electron-acceptor building block for donor–acceptor π-conjugated polymers for organic thin film transistors

Abstract

(3Z,3′Z)-3,3′-(Hydrazine-1,2-diylidene)bis(indolin-2-one) (HBI) containing an azine linkage is used as a novel amide-based π-conjugated electron-accepting building block for constructing donor–acceptor (D–A) π-polymer semiconductors. Copolymers of HBI and bithiophene are synthesized, which show small optical band gaps (∼1.6 eV) and quite low-lying highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels (E_HOMO = −5.6 eV; E_LUMO = −4.0 eV). The spin-coated polymer thin films are highly crystalline with a favoured edge-on lamellar chain packing motif, and exhibit high ambipolar charge transport performance with hole and electron mobilities up to 0.11 and 0.035 cm² V⁻¹ s⁻¹, respectively.