Studies on CH₃NH₃PbI₃ prepared by low-cost wet chemical technique

Methylammonium lead iodide (CH₃NH₃PbI₃) has attracted tremendous attention in solar cell development due to its direct band gap, ~ 1.50 eV and high optical absorption coefficient, ~ 10⁴–10⁵ cm⁻¹. CH₃NH₃PbI₃ samples were synthesized using a low-cost wet chemical technique and studied their structural, optical, morphological, compositional and thermogravimetric properties. X-ray diffraction pattern of CH₃NH₃PbI₃ revealed a single phase with tetragonal crystal structure; however, the orientation strongly depended on the heating of the sample. Raman spectra exhibited the bending and stretching bonds of Pb–I around 62 and 94 cm⁻¹, respectively, in all samples. The chemical functions of C–H and N–H stretching, C–H and N–H bends, O–H stretch and C–H rock and twist bonds were detected in FTIR spectra. A systematic bond shift revealed higher wavenumber upon increasing the drying temperature demonstrates the growth of stable material. A sharp band edge observed around 1.5 eV confirmed the synthesis of less defective material suitable for high efficiency solar cell development. The content of Pb and I with a desired stoichiometry was determined with EDS measurement. Thermogravimetric analysis demonstrates no weight loss in CH₃NH₃PbI₃ samples up to 220 °C.