Synthesis of New Indolocarbazole-Acceptor Alternating Conjugated Copolymers and Their Applications to Thin Film Transistors and Photovoltaic Cells

We report synthesis, properties, and optoelectronic device characteristics of six new indolocarbazole-acceptor Conjugated copolymers prepared by Suzuki coupling reaction. Two different linkages of indolocarbazole (28IC and 39IC) and four acceptors of 2,3-didodecylthieno[3,4-b]pyrazine (TP12), 2,3-bis(4-(2-ethylhexyloxy) phenyl)thieno[3,4-b]pyrazine (TPO), 2,1,3-benzothiadiazole (BT), and 2,3-bis(4-(2-ethylhexyloxy)phenyl)quinoxaline (QO) were used to explore the effects of acceptor structure, linkage, and side group on the electronic and optoelectronic properties. The optical hand gap (eV) of the Studied copolymers were in the following order: P28IC-TPO (1.58) < P39IC-TP12 (1.79) < P28IC-TP12 (1.84) < P28IC-BT (2.09) < P28IC-QO (2.31) < P39IC-QO (2.34). The hole mobility and on-off ratios of the studied copolymers were in the ranges 1.66 x 10(-5) to 4 x 10(-4) cm(2)/V.s and 40-46900, respectively. It basically depended on the degree of intromolecular charge transfer between indolocarbazole and acceptor as well as the HOMO level. The power conversion efficiency (PCE) of the indolocarbazole-acceptor polymer/PC61BM or PC71BM based photovoltaic cells were in the range 0.14-1.40% under the illumination of AM 1.5G (100 mW/cm(2)). P28IC-QO showed the best PCE among the Studied copolymers because of its Suitable HOMO/LUMO energy level, high molecular weight, good hole mobility, efficient PL quenching, and large V-oc.