TS Science

The all-inorganic lead halide perovskites, including cesium lead iodide (CsPbI3), have attracted significant attention due to their possible applications in photo voltaics, light-emitting devices, and other optoelectronic technologies, driven by their intrinsic optoelectronic properties. This study introduces a simple, green, and scalable solution synthesis method for the CsPbI3 perovskite fabrication, utilizing β-diketonate [Cs(hfa)]n and [Pb(hfa)2diglyme]2 precursors and ethanol as solvent. The as-synthesized nanoribbons are initially fabricated in the pure yellow δ-phase, as confirmed by X-ray diffraction and energy-dispersive X-ray analysis. Thermal analysis through differential scanning calorimetry highlights the reversible phase transition from δ-CsPbI3 to the black cubic α-phase. The photoactive and metastable black γ-CsPbI3 is obtained via high-temperature annealing and rapid cooling under inert conditions. Optical characterizations have been performed in order to extrapolate a bandgap of 2.89 eV for the δ-phase and 1.62eV for the γ-phase, while the photoluminescence analysis displays intense emissions at 530 and 700nm for the δ- and γ-phase, respectively. Ambient photoemission spectroscopy further elucidates the energy levels of the γ-phase, determining a highest occupied molecular orbital energy of 5.68 eV and a work function of 4.32eV. These findings demonstrate the possibility to syn thesize pure CsPbI3 and obtain the γ-CsPbI3 phase with promising applications.