Optical and Electrical Properties of Perovskite Variant (CH₃NH₃)₂SnI₆

In recent years, lead halide perovskites have emerged as excellent photovoltaic materials for solar power generation. However, because they are toxic and chemically unstable in air, lead-free perovskites are also being investigated. In this study, the perovskite variant (CH₃NH₃)₂SnI₆ was studied. Polycrystalline films of (CH₃NH₃)₂SnI₆ were prepared using the thermal evaporation method. The films had a direct band gap of 1.81 eV with a strong absorption coefficient of ∼7 × 10⁴ cm^–1. In addition, the films were n-type with a carrier concentration of ∼2 × 10¹⁵ cm^–3 and an electron mobility of ∼3 cm² V^–1 s^–1. Moreover, the conductivity was increased by a factor of 4 under simulated solar illumination (100 mW cm^–2). These results indicate that (CH₃NH₃)₂SnI₆ is a lead-free optical semiconductor suitable for solar cell applications.