Structure, optical and electrical properties of CH3NH3SnI3 single crystal

CH3NH3SnI3 crystals with largest size up to 10 mm × 6 mm × 6 mm were grown in aerobic environment using cooling crystallization method. XRD analysis of the crystal powder shows that the CH3NH3SnI3 crystal grown is of cubic phase with lattice constants a = b = c = 6.2480 Å. XRD and EDX results show that the chemical properties of CH3NH3SnI3 crystal are unstable in air, and the oxidation mechanism of CH3NH3SnI3 was analyzed. HRTEM shows that the CH3NH3SnI3 crystal grown is of good crystallinity. FT-IR spectrum of CH3NH3SnI3 crystal was identified. The band gap Eg of the CH3NH3SnI3 crystal is estimated to be 1.33eV according to the absorption spectrum. First-principles calculation shows the band gap of cubic CH3NH3SnI3 crystal is 1.36 eV, which is consistent with the experimental results. The thermal property of CH3NH3SnI3 is analyzed by TG/DTG analysis. Our results show that CH3NH3SnI3 crystal has potential application prospects in the field of solar cells, however its poor chemical stability in air, leading to the formation of SnI4 and SnO would limit its application in photoelectric fields.