Facile Route To Control the Ambipolar Transport in Semiconducting Polymers

Abstract

Control of electron and hole transport in conjugated molecules is a challenging but essential task for deeply understanding the intrinsic charge transport behaviors as well as technological benefits for optimizing the performance of various optoelectronic devices. Here we suggest a facile route to controlling ambipolar charge transport in conjugated polymers by precise regulation of the copolymerization ratio between a relatively large electron donor and acceptor building block as a repeating unit. By varying the ratio between poly[2,5-bis(2-octyldodecyl)pyrrolo [3,4-cpyrrole-1,4 (2H,SH)-dione-(E)-[2,2-bithiophen]-5-yl)-3-(thiophen-2-yl)a crylonitrile] (DPP-CNTVT) as an electron transport unit and DPP-selenophene-vinylene-selenophene (DPP-SVS) as a hole transport unit, mobility (mu(FET)) and onset voltage (V-on) in organic field-effect transistors are effectively modulated from p-channel [mu(FET,h) = 6.23 +/- 0.4 cm(2) V-1 s(-1)] to n-channel [mu(FET,e) = 6.88 +/- 1.01 cm(2) V-1 s(-1)] dominant transport. The same two DPP-based building blocks can lead not only to precise controllability of the transport mode but also significantly increased mobility without distortion of polymer backbone coplanarity. We also investigate bias stability of hole and electron in ambipolar transistors. Our methodology provides a new strategy for developing high-performance ambipolar polymer semiconductors for application in printed flexible integrated circuits and light-emitting transistors.