Conjugated copolymers based on dihexyl-benzimidazole moiety for organic photovoltaics

Abstract

In this study, we report the synthesis, characterization, and photovoltaic properties of a series of four conjugated polymers based on donor-acceptor (D-A) structure. New polymers, P1, P2, P3 and P4 utilizing a new accepter, dihexyl-2H-benzimidazole, were synthesized using Stille coupling reaction. Even with two bithiophene units in the copolymers to facilitate absorption at the longer wavelength, the incorporation of dihexyl-substituent on 2H-benzimidazole enables the polymers to have good solubility. The spectra of the solid films show absorption bands with maximum peaks at about 442-479 nm and the absorption onsets at 529-575 nm, corresponding to band gaps of 2.16-2.34 eV. The device with P4:PC71BM blend demonstrated an open-circuit voltage (VOC) of 0.59 V, a short-circuit current (JSC) of 6.43 mA/cm2, and a fill factor (FF) of 0.39, leading to the efficiency of 1.46%. © 2010.