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 ABX3, the perovskitoid has a second crystalline structure defined by A′B2X6, 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.