Abstract: Organic-inorganic halide perovskite (OIHP) materials through their promising material properties, simple solution processability, low material cost, high photon absorption, carrier mobilities, and tunable band gap are suitable for large area coatings in the fabrication of optical displays, LEDs, photovoltaic cells and photodetectors. However, OIHP stability and shelf life have been limited to date as exposed perovskite films do not survive long in ambient air causing further issues for large scale OIHP based device production and deployment. Accordingly, the inventors have established three-cation material system variants using an innovative single solution thiocyanate (SCN) doped three cation material system allowing tailoring of perovskite grain size and microstructure to minimize degradation from exposure to atmospheric conditions.