Influence of Acceptor Units with the Trifluoromethyl Group on Charge Transport in Donor–Acceptor Semiconducting Copolymer Films

Abstract

The authors report that the conversion of the charge-transfer characteristics in benzodithiophene‐thiadiazoloquinoxaline (BDT-TAQ)-based donor (D)‐acceptor (A) semiconducting copolymer, wherein the BDT moiety functions as the donor part and the TAQ block functions as the acceptor unit, is possible by adding trifluoromethyl groups to the TAQ-acceptor unit. The charge-transport characteristics of the BDT-TAQ films were investigated using a transistor platform, where the semiconducting films served as the active channel layer. The BDT-TAQ-based polymeric thin-film transistors (PTFTs) clearly show ambipolar characteristics that enable both electron and hole transport in the semiconducting polymer channel. By contrast, the PTFTs with BDT-TAQ-CF3 as an active layer exhibit only n-type transport characteristics. These results suggest that the trifluoromethyl groups added to the acceptor unit of the BDT-TAQ-based D‐A semiconductor copolymer change (reduce) the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the semiconductor copolymer film.