Synthesis of Cs₂SnI₆ perovskite thin film by low-pressure chemical vapor deposition method

Cs₂SnI₆ is an all-inorganic, air-stable and Pb-free halide perovskite material. In this work, we propose a low-pressure chemical vapor deposition method that enables the synthesis of continuous Cs₂SnI₆ thin films. Some technical parameters such as the deposition time and the deposition temperature of CsI were varied to investigate the morphology and thickness of Cs₂SnI₆ thin films. The film was further undergone an annealing treatment in SnI₄ ambient to enhance characteristics, such as the long-term stability and the structural, optical and electrical properties. After annealing in SnI₄, the film was found to be stable in ambient air (40–60% humidity) for 30 days. The film shows n-type semiconducting with an energy bandgap of 1.58 eV. Its absorption coefficient is higher than 3.4 × 10⁴ cm⁻¹ in the visible region with a maximum value of 0.9 × 10⁵ cm⁻¹ at the wavelength of 420 nm. The carrier concentration increased to 5.5 × 10¹⁷ cm⁻³, and the resistivity declined to 3.1 Ω.cm.