Temperature-dependent photoluminescence of Co-evaporated MAPbI3 ultrathin films

The hybrid organic-inorganic perovskite (PVK) thin films have attracted amounts of interest in the past decade due to the thickness-depended quantum confinement effects and tunable band gap as well as the demands of device miniaturization. Vacuum deposition is a promising method to realize precise control of film thickness and composition, low-temperature processing, the good compatibility with dry processing and compatible with the modern silicon-based semiconductor industry. Here, we report on the temperature-dependent photoluminescence properties of MAPbI(3)& nbsp;ultrathin films with long-term stability and high quality fabricated by the co evaporation. XPS, AFM and XRD results reveal that an excess MAI vapor environment plays a key role in sample preparation. PL is more sensitive than XPS to detect trace MAPbI(3)-like materials with strong luminescence properties. Temperature-dependent PL measurements show that the bandgap of MAPbI(3) films red-shifted with the temperature decreasing in the range from 298 to 78 K, which is opposite to that of the traditional semiconductors and can be attributed to the interaction between the electron-phonon and the thermal expansion induced band gap renormalization. Gradual phase transition from tetragonal one to orthorhombic one is observed to start between 108 and 118 K, which is lower than the reported sudden phase transition temperature of 150 K for bulk MAPbI(3) and suggests the important role of quantum confinement in ultrathin films. Our findings provide a way to fabricate PVK ultrathin films with long-term stability for novel light emitting devices.

Automated summary

Hybrid organic-inorganic perovskite (PVK) thin films have attracted significant attention due to their tunable band gap and thickness-dependent quantum confinement effects. Vacuum deposition is a promising method for precise control of film thickness and composition. In this study, we fabricated long-term stable and high-quality ultrathin MAPbI(3) films using co-evaporation and investigated their temperature-dependent photoluminescence properties. Our findings suggest the importance of excess MAI vapor in sample preparation and provide insights into the bandgap and phase transition behavior of ultrathin PVK films.