Solution‐Processed Small‐Molecule Bulk Heterojunction Ambipolar Transistors

Abstract

Solution‐processed small‐molecule bulk heterojunction (BHJ) ambipolar organic thin‐film transistors are fabricated based on a combination of [2‐phenylbenzo[ d , d ']thieno[3,2‐ b ;4,5‐ b ']dithiophene (P‐BTDT) : 2‐(4‐ n ‐octylphenyl)benzo[ d , d ']thieno[3,2‐ b ;4,5‐ b ']dithiophene (OP‐BTDT)] and C 60 . Treating high electrical performance vacuum‐deposited P‐BTDT organic semiconductors with a newly developed solution‐processed organic semiconductor material, OP‐BTDT, in an optimized ratio yields a solution‐processed p ‐channel organic semiconductor blend with carrier mobility as high as 0.65 cm 2 V −1 s −1 . An optimized blending of P‐BTDT:OP‐BTDT with the n ‐channel semiconductor, C 60 , results in a BHJ ambipolar transistor with balanced carrier mobilities for holes and electrons of 0.03 and 0.02 cm 2 V −1 s −1 , respectively. Furthermore, a complementary‐like inverter composed of two ambipolar thin‐film transistors is demonstrated, which achieves a gain of 115.