Characterization of methylammonium tin iodide thin films prepared by sequential physical vapour deposition

Methylammonium tin triiodide (MASnI3) films were grown through Sequential Physical Vapour Deposition (SPVD) without breaking the vacuum and optimized by varying MAI thickness and annealing time while keeping SnI2 thickness constant. The film's crystallinity increased with MAI thickness and annealing time. Optimal bandgap was attained for the film with 500 nm MAI annealed for 20 & 40 min. FE-SEM revealed densely packed, large grains, increasing in size with MAI thickness and on annealing from 0 to 40 min and decreasing at 80 min. The film with 300 nm MAI thickness annealed for 40 min showed the strongest PL intensity suggesting reduced carrier recombination losses. Trap densities reduced with annealing time and MAI thickness due to improvements in films' crystallinity, grain sizes and reduced grain boundaries which act as carrier trapping sites. Hence, films prepared through SPVD, exhibit excellent structural, optical, and morphological properties, suitable for photovoltaic applications.