Main-chain polyoxometalate-containing donor–acceptor conjugated copolymers: synthesis, characterization, morphological studies and applications in single-component photovoltaic cells

Abstract

Two new organic–inorganic hybrid conjugated copolymers (P10 and P11), containing different amounts of hexamolybdate clusters covalently embedded in the main chain with imide-functionalized naphthodithiophene and 3,3′-didodecyloxy bithiophene units, have been synthesized and characterized in detail. The incorporation of hexamolybdate clusters into the polymer backbones is confirmed by ¹H NMR, FT-IR, gel permeation chromatography, and elemental analysis. These hybrid copolymers are capable of forming uniform thin films upon spin coating, and they show intense visible and broad near-infrared (NIR) absorptions both in CHCl₃ solutions and as spin-casted thin films. Single-component solar cells based on P10, without any other added electron acceptors, show respectable power conversion efficiencies up to 0.31%. The photocurrent contribution from both the organic π-segments and the POM clusters is confirmed by the incident photon-to-current conversion efficiency measurements. The absorption in the NIR region is found to be incapable of producing photocurrent, and the photocurrent of the solar cells is attributed exclusively to the UV and visible absorptions of the hybrid copolymers.