Methods for Manufacturing Highly Efficient Wide-Gap Perovskite Solar Cells

The present disclosure relates to a device that includes a layer that includes a perovskite, where the layer has a first side and a second side defining a thickness, the perovskite has a bulk composition as defined by AB(X.sub.1-yX.sub.y').sub.3, where A includes a first cation, B includes a second cation, X includes iodide, and X' includes bromide, y is between 0.2 and 0.8, inclusively, and the thickness has a bromide concentration gradient across the thickness with a maximum concentration at or in the proximity of the first side and a minimum concentration at the second side.