Synthesis and study of low-bandgap polymers containing the diazapentalene and diketopyrrolopyrrole chromophores for potential use in solar cells and near-infrared photodetectors

The two pairs of structurally related donor-acceptor polymers (P1-P4) derived from diketopyrrolopyrrole (DPP) and diazapentalene (DAP) building blocks were synthesized and compared for their optical and photovoltaic properties with potential applications in solar cells and near-infrared (NIR) photodetectors. Having the electron-rich fluorene and bis(2'-thienyl)pyrrole (TPT) units as donors, the synthesized donor-acceptor polymers have band gap levels in the range 1.22-1.79 eV. The solar cells based on the blend of P2 (DPP-TPT polymer) and PC71BM exhibited the best performance, showing a V-oc of 0.61 V, J(sc) of 10.38 mA cm(-2), FF of 0.44 and PCE of 2.8%. The photodetector based on the NIR-absorbing P4 (DAP-TPT polymer) displayed a good photovoltaic response over a wide spectral range of 400-1100 nm and an EQE of 13% and detectivity of 2.3 x 10(10) Jones at 800 nm.