Improved oxidation stability of tin iodide cubic perovskite treated by 5-ammonium valeric acid iodide

Tin iodide cubic perovskite, CH3NH3SnI3, is a promising light absorbing material for perovskite solar cells. However, this compound is known to be unstable in air. According to a previous paper, CH3NH3SnI3 partially decomposes within 2 h before total decomposition after 1d. We prepared CH3NH3SnI3 with the addition of 5-ammonium valeric acid iodide (5-AVAI). In CH3NH3PbI3, 5-AVAI was known to improve the power conversion efficiency and stability by forming (5-AVAI)x(CH3NH3)1−xPbI3. Powder X-ray diffraction analysis revealed that the tin iodide cubic perovskite structure is maintained irrespective of the addition of 5-AVAI, which differs from the behavior of CH3NH3PbI3 perovskite. Moreover, the addition of 5-AVAI significantly improved the oxidation stability of the material in the air.