Temperature and Light Modulated Open‐Circuit Voltage in Nonfullerene Organic Solar Cells with Different Effective Bandgaps

Abstract The relationship of the temperature–light intensity dependence of open‐circuit voltage V_oc in nonfullerene‐based organic solar cells with their material characteristics and multimechanism recombination parameters is described. The systematic variation of the effective bandgap E_g,eff and the electrode layers allows the observation of different relative contributions of bimolecular, bulk, and surface trap‐assisted recombination mechanisms. The complementary advantages of the analytical model and the established voltage‐impedance spectroscopy technique provide a useful tool to quantify multimechanism recombination parameters, effective density of states N_c, and energetic disorder σ in organic solar cells under operating conditions. The validity of the proposed model to understand the temperature and light intensity dependent of V_oc is shown by applying it to four different donor:nonfullerene acceptor blend systems with conventional or inverted device architectures.