Study of Perovskite Thin Films CH3NH3PbICl2: Synthesis, Structure, and Optical Properties

In this work, thin films of hybrid organic-inorganic perovskite CH3NH3PbICl2 are successfully synthesized by a two-step method involving the preparation of methylammonium iodide (CH3NH3I) followed by interaction with PbCl2. The surface morphology of the films is studied by optical microscopy and atomic-force microscopy (AFM), which reveals a uniform granular structure with particle sizes in the range of 90–200 nm. X-ray diffraction (XRD) analysis confirmed the formation of a predominantly tetragonal phase of CH3NH3PbICl2. Fourier-transform infrared spectroscopy (FTIR) reveals the characteristic vibrational modes of the methylammonium cation (CH3N $${\text{H}}_{3}^{ + }$$ ), and ultraviolet–visible (UV–Vis) spectroscopy shows a pronounced excitonic absorption edge at ~760 nm and a band gap of Eg ≈ 1.54 eV. Photoluminescence measurements show an intense peak at 750 nm, which indicates high crystallinity and a low defect concentration. The introduction of Cl− ions into the crystal lattice causes a blue shift in the absorption and luminescence spectra, which suggests improvement in the morphology and ordering of the structure. The obtained results confirm the potential of CH3NH3PbICl2 perovskite for use in photonic and photovoltaic devices.