Effect of Annealing Temperature on the Formation of Methyl Ammonium Tin Tri-Iodide Perovskite Thin Film

Abstract

Organic-inorganic perovskite photovoltaics (PVs) have attracted a lot of attention as high- efficiency thin film PVs which are relatively cheap and easy to fabricate. Lead halide perovskites have shown a rapid rise in power conversion efficiency by 3.8 % in 2009 to 21.02 % in 2016. One major problem is that lead is toxic and poses a serious concern to health and the environment. The most likely substitute for lead is tin. Tin-based perovskite solar cells have shown good semiconducting properties but still have very low efficiencies. The major challenge is the instability of tin in its +2 oxidation state. The photovoltaic performance and life span of these solar cells depend greatly on the film morphology. The morphology depends on the deposition technique and the subsequent treatment employed. In this work, we investigated the effect of post annealing temperature on the formation of methyl ammonium tin tri-iodide (CH 3 NH 3 SnI 3 ). The SnI 2 /CH 3 NH 3 I was formed by sequential thermal evaporation of SnI 2 followed by evaporation of CH3NH3I on a glass substrate. As-deposited SnI 2 /CH 3 NH 3 I films on glass substrate are annealed at different temperatures (80 o C, 90 o C, 100 o C, 110 o C, and 120 o C) in nitrogen atmosphere. Resistivity measurements and X-ray Diffraction (XRD) show that the best annealing temperature range for the formation of CH 3 NH 3 SnI 3 may be between 80 o C and 100 o C.