Probing the defects states in MAPbI3 perovskite thin films through photoluminescence and photoluminescence excitation spectroscopy studies

The luminescence properties of methylammonium lead iodide (MAPbI3) perovskite thin films deposited on corning 1737 glass substrates are studied using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy. From the PL spectra analysis, it is realized that there are two emission peaks, a high-intensity peak at 1.58 eV (~783 nm) and a smaller shoulder peak at 1.64 eV (~754 nm) in the bandgap energy region. The peak at ~1.64 eV corresponds to the bandgap of MAPbI3, whereas the high-intensity peak at photon energy ~1.58 eV is due to the presence of shallow trap states. The calculated optical bandgap energy 1.58 ± 0.01 eV is close to the reported bandgap energy 1.60–1.61 eV and consistent with the PL peak position. The slight difference in bandgap value is due to shallow defect states in MAPbI3 films. The slow decay of photocurrent observed in the transient photocurrent measurements further confirms the presence of shallow trap states in MAPbI3 perovskite.