Near-infrared photovoltaic performance of conjugated polymers containing thienoisoindigo acceptor units

Abstract

Donor-acceptor-type conjugated copolymers containing a thienoisoindigo unit are synthesized and characterized. In combination with benzodithiophene donor units, this strong acceptor moiety can be used to extend the light absorption of their conjugated copolymers to longer wavelengths. The absorption spectra of the copolymers show features that extended up to 1200 nm in the near infrared (NIR). The resulting optical energy gaps are very narrow, ranging from 1.20 to 1.29 eV. The copolymers are used as the donor material with PC61BM acceptor in the active layer of bulk-heterojunction organic photovoltaic cells, and the devices exhibit photocurrent at NIR wavelengths with a power-conversion efficiency of 0.52% under air mass (AM) 1.5 illumination. NIR-absorbing donor-acceptor-type polymers containing the thienoisoindigo unit are synthesized. The UV-vis spectra of the polymers show features that extended up to 1200 nm in the NIR. The organic photovoltaic cells using the synthesized polymers show a photocurrent response in the NIR with power conversion efficiency up to 0.52% under AM 1.5 photo irradiation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.