Synthesis and characterization of polypyrrole encapsulated formamidinium lead bromide crystals for fluorescence memory recovery

• Smart material synthesis through polymer encapsulated perovskite crystals. • The materials are used for Memory Recovery application. • The role of a conducting polymer in offering better emission quality and stability of the perovskite crystals. • Impressive optical properties of polymer-perovskite composite make the material for optoelectronic devices. Impressive optical properties of organic–inorganic lead halide perovskite crystals make them suitable for optoelectronic devices. However, these crystals are unstable in water and other polar solvents and quickly lose their fluorescence which cannot be recovered by the addition of non-polar solvents. Fluorescence recovery is absolute necessity for long-term stability of perovskite in optoelectronic devices. Till date, there is no report showing mechanism of fluorescence recovery of organic–inorganic lead halide perovskite crystals. Here, we have reported the synthesis of FAPbBr 3 /polypyrrole (PPy) composites (FA = Formamidinium) for shedding light on the mechanism of fluorescence recovery in presence of N,N Dimethyl formamide or DMF. We have synthesized FAPbBr 3 crystals at room temperature and tuned their band gap from green to blue by varying the amount of surfactant. Similar study was repeated with FAPbBr 3 /PPy composites, synthesized through in situ polymerization. Encapsulation was found to improve the emission quality and purity of the colour and successfully restored the fluorescence memory which was lost in presence of DMF. The recovery was attributed to resurfacing of PPy in presence of toluene which brought the building blocks of FAPbBr 3 crystals back to the co-crystallization domain. In brief, this fundamental finding could pave the future way for achieving long-term stability of perovskite crystals in optoelectronic devices.