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

• Published in: Advanced energy materials 2024-03, Vol.14 (12), p.n/a
• Main Authors: Remmerswaal, Willemijn H. M., Gorkom, Bas T., Zhang, Dong, Wienk, Martijn M., Janssen, René A. J.
• Format: Article
• Language: English
• Subjects: absolute photoluminescence; Charge transport; Current carriers; Electric potential; Electron transport; Energy gap; Energy levels; Luminous intensity; Metal halides; metal‐halide perovskite; passivation; Passivity; Perovskites; Photoelectric effect; Photoluminescence; Photovoltaic cells; quasi‐Fermi level splitting; Radiative recombination; Solar cells; Spectrum analysis; Voltage
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202303664

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. Quasi‐Fermi level splitting experiments reveal that open‐circuit voltage losses in wide‐bandgap perovskites primarily occur at the interface between the perovskite and the electron selective contact. Passivation reduces these losses. Interestingly, passivation does not improve the energy level alignment or the perovskite surface. Instead, passivation involves reducing the spatial distance between the perovskite semiconductor and the electron transport layer.