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

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AbstractWide‐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.