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

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,E-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 sigma 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.