New Two-Dimensional Thiophene−Acceptor Conjugated Copolymers for Field Effect Transistor and Photovoltaic Cell Applications

Abstract

We report the synthesis, properties, and optoelectronic device applications of two-dimensional (2D) like conjugated copolymers, P4TBT, P4TDTBT, P4TDTQ, and P4TDPP, consisting of 2′,5′′-bis(trimethystannyl)-5,5′′′-di-(2-ethylhexyl)[2,3′;5′,2′′;4′′,2′′′]quarterthiophene (4T) with the following four acceptors of 4,7-dibromo-2,1,3-benzothiodiazole (BT), 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTBT), 2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,8-bis[5′-bromodithien-2-ylquinoxalines] (DTQ), and 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP). The optical band gaps (eV) of the studied conjugated copolymers are in the order of P4TDPP (1.29) < P4TDTBT (1.60) < P4TDTQ (1.83) < P4TBT (1.88). The 2D-like conjugated copolymers exhibited high field effect (FET) hole mobilities in the range of 10−1−10−4 cm2 V−1 s−1. On the other hand, the FET electron mobilities were observed for P4TDTBT and P4TDPP because of their relatively low-lying LUMO level suitable for electron injection. In par...