Halide perovskite materials have emerged in the past few years as novel materials for use in the active layer of heterojunction photovoltaic cells and new emissive layers in light emitting diode (LED) displays. In photovoltaic applications they promise to lower costs, and improve efficiency of commercial photovoltaic cells. Their low temperature processability may also lead to interesting new applications in existing solar cell technologies. In LED applications, they exhibit other desirable properties such as color tunability, simple device structures, and facile processability. Although they exhibit many desirable properties, there are still challenges that must be overcome before commercialization can be realized such as observed hysteresis, and short operational lifetimes. In this work it is shown that these issues can be overcome by using a deterministic nucleation process. Using a patterned transition metal nucleation promoter, it is shown that grain size can be controlled on silicon and indium tin oxide substrates. This process can be adopted to many different perovskite systems and produces large and extremely uniform grains. These grains exhibited superior stability compared to nanocrystalline films, and had no observed hysteresis effects. Using these large grain perovskites, photodetectors and single layer LEDs are fabricated.