Alternating copolymers of carbazole and triphenylamine with conjugated side chain attaching acceptor groups: Synthesis and photovoltaic application

Abstract

Four alternating copolymers of carbazole (Cz) and triphenylamine (TPA) with thienylenevinylene (TV) conjugated side chain containing different acceptor end groups of aldehyde (PCzTPATVCHO), monocyano (PCzTPA-TVCN) dicyano (PCzTPA-TVDCN), and 1,3-diethyl-2-thiobarbituric acid (PCzTPA-TVDT), have been designed and synthesized. The structures and properties of the main chain donor-side chain acceptor D-A copolymers were fully characterized. Through changing the acceptor group attached to the TV conjugated side chain on TPA, the electronic properties and energy levels of the copolymers were effectively tuned. The effect of substituent on the electronic structures of the copolymers was also studied by molecular simulation. These results indicate that it is a simple and effective approach to tune the bandgap in a conjugated polymer by attaching an acceptor end group on the conjugated side chains. PCzTPA-TVCN, PCzTPA-TVDCN, and PCzTPA-TVDT were used as donor in polymer solar cells; the device based on PCzTPA-TVDT/PC70BMdemonstrates a power conversion efficiency of 2.76% withVoc of 0.87 V under the illumination of AM1.5G, 100 mW/cm2. © 2010 American Chemical Society.