Photoluminescence lifetime of perovskites on modified substrates

Lead halide perovskites have gained attention for their potential in optoelectronic applications, including photovoltaics and light-emitting devices, due to their remarkable optical and electronic properties. However, performance of these materials is highly dependent on morphological properties of the underlying substrates. In this study, the effects of substrate modifications on the photoluminescence lifetimes of CsPbBr₃ perovskites deposited on TiO2 substrates that were annealed at various temperatures were investigated. TiO2 substrates were characterized using glancing-angle x-ray diffraction and spectroscopic ellipsometry to assess changes in crystallinity and surface roughness. Time-correlated single photon counting spectroscopy was employed to measure the photoluminescent lifetimes of the perovskites. Scanning electron microscopy and x-ray diffraction were used to determine morphology and crystallinity. Results show a clear relationship between substrate annealing temperature and the photoluminescent lifetime of perovskite microcrystals. Substrates annealed at temperatures below 300 °C exhibited increased surface roughness with increased annealing temperature (22.4 Ȧ at room temperature and 48.05 Ȧ at 300 °C) and correspondingly shorter photoluminescent lifetimes (3.5 ns at room temperature and 0.4 ns at 300 °C) suggesting more rapid charge carrier recombination. In contrast, substrates annealed at 350 °C exhibited the longest lifetimes at 4.19 ns indicating a decrease in trap-mediated nonradiative recombination. Substrates annealed at 400 °C showed a further increase in crystallinity but did not extend the lifetime beyond that seen at 350 °C, suggesting an optimal balance between surface roughness and crystallization. These findings provide insights into the role of morphological substrate modifications in optimizing the optoelectronic properties of perovskite materials.