LAUSR

Hybrid perovskites demonstrate high potential in optoelectronic applications. Their main drawback is their low stability under humid conditions. In this paper, one of nature's strategies is implemented—the incorporation of amino acids into the crystal lattice—in order to improve the stability of methylammonium lead bromide (MAPbBr3) in water, and to tune its structure, as well as its optical and thermal properties. The amino acid lysine, which possesses two NH3+ groups, is incorporated into the hybrid unit cell, by substituting two methylammonium ions and serves as a “molecular bridge”. This incorporation induces a decrease in the lattice parameter of the host, accompanied with an increase in its bandgap and noticeable changes in its morphology. Furthermore, a substantial decrease in the thermal expansion coefficient of MAPbBr3 and a shift of its cubic‐to‐tetragonal phase transformation temperature are observed. Two different modes of incorporation are identified, which depend on the conditions of crystallization. These modes dictate the level of lysine incorporation and the magnitude of MAPbBr3 bandgap changes. Notably, lysine incorporation strongly increases the perovskite stability in water. This study demonstrates a unique and promising approach to tune the properties and improve the stability of hybrid perovskites via this novel bioinspired route.