Compositions and Methods for Modifying Perovskite Surfaces

The present disclosure relates to a composition that includes a first layer that includes a perovskite and a second layer that includes a perovskitoid, where the perovskite has a first crystalline structure defined by ABX.sub.3, the perovskitoid has a second crystalline structure defined by A'B.sub.2X.sub.6, where A is a first cation, B is a second cation, X is an anion, and A' is a third cation having either a 1+ charge or a 2+ charge.