Characterization of Sn(II)-based Perovskites by XRD, DTA, NQR and 119Sn NMR for Photovoltaic Applications

One of the most anticipated candidates for lead-free halide perovskite for photovoltaic applications is Sn(II)-based halide. In this report four perovskites CH3NH3SnBr3, CH(NH2)(2)SnBr3, CH3NH3SnI3 and CH(NH2)(2)SnI3 were characterized by DTA, XRD, Br-81, (127)INQR and Sn-119 NMR. A new synthetic approach was also proposed for the bromide analogs, in which only pure water was used as a solvent. Although, these four crystals belong to a cubic system at ambient temperature, only CH(NH2)(2)SnBr3 showed a large lattice constant (a approximate to 2a(c)) in which an isolated SnBr3- anion was confirmed. In order to detect Sn-119 NMR, the addition of reduced agent SnF2 was considerably effective to remove the high-frequency shift (Knight shift) and the broadening due to the half-metallic conductivity of the as-grown crystals.