Passivation of Organic–Inorganic Hybrid Perovskite with Poly(lactic Acid) to Achieve Stable Red-Light Flexible Films

Low-dimensional organic–inorganic hybrid perovskites (OIHPs) have shown significant potential in the optoelectronic field due to their adjustable structure and properties. However, the poor air stability and flexibility of the OIHP crystals limit their further development. Herein, three OIHP crystals have been synthesized using cadmium chloride and the isomer of phenylenediamine as raw materials. Mn2+ doping turns on the red-light emission of Cd-based OIHPs at around 625 nm. Interestingly, the organic ligands with different steric hindrance can induce a transition of the OIHP structure from two dimensions (2D) to one dimension (1D), thereby regulating the quantum yield of red luminescence in the range of 38.4% to nearly 100%. It is found that the surface-exposed amino groups are easy to oxidize, resulting in the instability of these OIHP crystals. Therefore, poly(lactic acid) (PLA) is selected to passivate OIHPs through hydrogen bonding between CO of PLA and –NH2 on the surface of OIHPs. As a result, the production of OIHP-based flexible films with highly efficient and stable red emission can be obtained after being encapsulated by PLA. They demonstrate enormous application potential in flexible X-ray imaging. This study not only realizes stable perovskite films but also provides an effective design idea for red flexible scintillators