Low-Bandgap DPP-Based Quinoxaline with Extended EQE and Low Energy Loss for Efficient Polymer Solar Cells

In this study, we have designed and synthesized a low-bandgap polymer, DPP-Qx, using quinoxaline (Qx), a non-alkylated weak acceptor, with diketopyrrolopyrrole (DPP) as an electron donor. The incorporation of Qx into DPP leads to the highest occupied molecular orbital level at −5.1 eV with a narrow optical bandgap (1.25 eV). The synthesized polymer is utilized in photovoltaics, and the photovoltaic properties are studied. This DPP-Qx with fullerene acceptors in polymer solar cells (PSCs) exhibits efficiency of 3.26%. Moreover, a minimum energy loss of 0.57 eV along with high extended external quantum efficiency is achieved with the DPP-Qx electron donor. The thermal, electrical and optical properties, energy levels and hole mobility of the synthesized polymer are studied and discussed.