Quantifying Non-Radiative Recombination in Passivated Wide-Bandgap Metal Halide Perovskites Using Absolute Photoluminescence Spectroscopy

Wide-bandgap (>1.6 eV) mixed-halide perovskites tend to experience notable open-circuit voltage losses in solar cells due to non-radiative recombination. Here, the effects of defects and their passivation on the non-radiative recombination of charge carriers in mixed-halide perovskite solar cells are studied. By determining the quasi-Fermi level splitting via absolute photoluminescence measurements of perovskite layers with and without charge transport layers, bulk and interface contributions are disentangled and compared to the radiative open-circuit voltage. For wide-bandgap perovskites, non-radiative recombination present in the pristine perovskite layers increases with increasing bandgap. The most prominent loss, located at the perovskite - electron transport layer interface (ETL), can be reduced by interface passivation for the different bandgaps studied (1.58 to 1.82 eV) to a level close to that of the intrinsic losses. By combining light-intensity-dependent absolute photoluminescence spectroscopy with sensitive spectral photocurrent measurements it is found that different passivation agents result in a similar decrease of the non-radiative recombination for different bandgaps. This suggests that the gained open-circuit voltage is not due to an improved energy level alignment at the perovskite - ETL interface. Instead, passivation involves eliminating the direct contact between the perovskite semiconductor and the ETL.