Composition-Driven Structural, Optical, Thermal and Electrochemical Properties of Hybrid Perovskite-Structured Methylammonium-Tin-Chloride

Compositional techniques are recognised as an efficient way to produce efficient and stable organic-inorganic halide perovskites (OIHPs). Several studies on OIHPs have criticized the instability and toxicity of lead, which have been largely overlooked due to the lack of large-scale commercial implementation. Tin-based OIHPs have been employed with three different perovskite systems to solve this problem. In this work, we report the synthesis and structural, optical, electrochemical and thermal properties of three different lead-free methylammonium tin chlorides, namely CH₃NH₃SnCl_3, CH₃NH₃Sn₂Cl₅ and (CH₃NH₃)₄SnCl₆. The synthesised perovskites were characterised by x-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL), thermogravimetric analysis (TGA) and cyclic voltammetry (CV) measurements. The analysis confirms that they have cubic, tetragonal and trigonal crystal structures. FE-SEM images showed agglomeration shapes. The DRS UV–Vis studies revealed that all the synthesised perovskites exhibit semiconducting behavior. PL analysis confirmed the emission centre in the green part of the spectrum. The thermal kinetics, including activation energy, Arrhenius constant, entropy, enthalpy and Gibbs energy, were calculated using the first weight loss of the TGA spectrum. CV analysis was used to determine the maximum specific capacitance of the supercapacitors, and revealed that the CH₃NH₃Sn₂Cl₅ perovskite exhibited better performance than CH₃NH₃SnCl₃ and (CH₃NH₃)₄SnCl₆ perovskites.