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.