Revisiting Sub-Band Gap Emission Mechanism in 2D Halide Perovskites: The Role of Defect States

• DOI: 10.1021/jacs.4c06621
• Publication Date: 2024-08-08T11:45:41Z
• Authors: Igal Levine; Dorothee Menzel; Artem Musiienko; Rowan MacQueen; Natalia Romano; Manuel Vasquez-Mo...; Eva Unger; Carlos Mora Perez; Aaron Forde; Amanda J. Neukirch; Lars Korte; Thomas Dittrich
• Keywords: Charge carrier

Understanding the sub-band gap luminescence in Ruddlesden–Popper 2D metal halide hybrid perovskites (2D HaPs) is essential for efficient charge injection and collection optoelectronic devices. Still, its origins are still under debate with respect to role of self-trapped excitons or radiative recombination via defect states. In this study, we characterized separation, recombination, transport single crystals, exfoliated layers, polycrystalline thin films butylammonium lead iodide (BA2PbI4), one most prominent HaPs. We combined complementary defect- exciton-sensitive methods such as photoluminescence (PL) spectroscopy, modulated time-resolved surface photovoltage (SPV) constant final state photoelectron yield spectroscopy (CFSYS), light-induced magneto (CLIMAT), demonstrate striking differences between separation induced by dissociation excitation mobile carriers from Our results suggest that broad emission BA2PbI4 other HaPs caused states (shallow well midgap states) rather than excitons. Density functional theory (DFT) show common defects can readily occur produce an energetic profile agrees experimental results. The DFT formation iodine interstitials initial process leading degradation, responsible emergence states, engineering will play a key enhancing properties future.