Polythiophene derivatives functionalized with maleimide moiety as pendant for bulk heterojunction photovoltaic cells

A series of polythiophene derivatives comprising maleimide moieties as repeating units in backbones (MPTM10) or as pendants (SPTM41 and SPTM21) were synthesized for use as photoenergy conversion materials in polymer solar cells (PSCs). The PSCs were fabricated from the blends of these maleimide-incorporated polythiophene derivatives and [6, 6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). A red shift of the maximum absorption wavelength was observed for the triphenylamine-maleimide functionalized side-chain type polythiophene derivatives SPTM41 and SPTM21 as compared with the maleimide-incorporated main-chain type MPTM10. Moreover, full-widths at half-maximum of UV–vis absorption bands of SPTM41 and SPTM21 were much larger than that of MPTM10. Therefore, the photovoltaic performances of PSCs based on the SPTM21/PCBM and SPTM41/PCBM blends were superior to those based on the MPTM10/PCBM blends. Among various fabricated materials, the greatest short-circuit current density (3.84 mAcm⁻²) and photoenergy conversion efficiency (0.37 %) were obtained for the SPTM21/PCBM blend-based PSC.