Effects of ambient exposure on photoluminescence of Dion-Jacobson tin-based halide perovskites

Tin-based halide perovskite materials are of interest for light-emitting applications due to their broad yellow emission, but they are known to exhibit inferior stability compared to lead-based perovskites due to the tendency of Sn2+ to be readily oxidized. Here, we investigated the ambient stability of a Dion-Jacobson tin bromide perovskite. We found that the optical properties of the samples were more significantly affected by moisture rather than the ratio of Sn2+/Sn4+. The exposure to humidity resulted in changes in the ratio of 2D HDASnBr(4) and hydrated 1D HDA(3)SnBr(8) phases (where HDA denotes hexane-1,6-diammonium), with an initial increase (up to similar to 40 h) in luminescence attributed to the increasing fraction of the hydrated 1D phase which contributes to self-trapped exciton emission. With further exposure to humidity, the material starts to degrade resulting in reduced luminescence after similar to 40 h. The use of additives for the suppression of oxidation of Sn2+, namely SnCl2 and tetraethyl orthosilicate (TEOS), results in prolonging the lifetime of the samples (>260 h for thin films with additives, compared to 180 h for thin films without additives). However, the persistence of luminescence with an increased time of ambient exposure in samples prepared with additives can be attributed to the changes in the evolution of phase compositions (ratios of 2D and hydrated 1D phases) over time rather than suppression of the oxidation of Sn2+.