Bio-Inspired Molecular Bridging in a Hybrid Perovskite Leads to Enhanced Stability and Tunable Properties

Hybrid organic-inorganic halide perovskites demonstrate high potential in several applications such as solar cells, field-effect transistors, light-emitting diodes and more. However, the main drawback which limits their use in such applications is their low stability in humid conditions. In this paper we implement one of Natures strategies found in bio-crystals in order to improve the stability of the hybrid perovskite methylammonium lead bromide (MAPbBr3) in water, as well as to tune its structure, optical and thermal properties. This was achieved, for the first time, by the incorporation of amino acids into the lattice of MAPbBr3. 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 the band gap and noticeable changes in its morphology. Furthermore, we observed a substantial decrease in thermal expansion coefficient and a shift of the cubic-to-tetragonal phase transformation temperature of the MAPbBr3 crystal. The level of amino acid incorporation depends on the conditions of crystallization, which also influence the extent of MAPbBr3 band gap changes. Notably, lysine incorporation at elevated temperature 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 bio-inspired route.