Realizing n-Type Field-Effect Performance via Introducing Trifluoromethyl Groups into the Donor–Acceptor Copolymer Backbone

Abstract

Developing a new strategy to obtain n-type organic semiconductors is crucial for the advance of organic electronics. We herein report the synthesis and investigation of a series of donor–acceptor-type diazaisoindigo-based copolymers, named PAIID-TFBVB-C1, PAIID-TFBVB-C3, and PAIID-BVB-C3. After introduction of the trifluoromethyl groups with strong electron-withdrawing ability into the molecular backbone of PAIID-BVB-C3-containing stilbene units, the obtained polymer PAIID-TFBVB-C3 shows obvious blue-shifted UV–vis absorption profiles because of the enlarged band gap revealed by the theoretical simulation. Meanwhile, both the energy levels of the lowest unoccupied molecular orbital (LUMO) of PAIID-TFBVB-C1 and PAIID-TFBVB-C3 with trifluoromethyl groups are lower than that of PAIID-BVB-C3 without trifluoromethyl groups, reducing the energy difference between the LUMO energy level and the work function of the source-drain electrode and further facilitating electron injection. Consequently, both the PAIID-TFBVB-C1- and PAIID-TFBVB-C3-based devices show typical n-type field-effect performance with electron mobilities of 0.11 and 0.04 cm2 V–1 s–1, respectively, whereas devices based on PAIID-BVB-C3 exhibit p-type semiconducting performance with a hole mobility of 0.14 cm2 V–1 s–1. Our results demonstrate that it is a feasible strategy to acquire n-type semiconducting materials by introducing the electron-withdrawing trifluoromethyl groups into the polymer backbone.