Underestimated effect of the polymer encapsulation process on the photoluminescence of perovskite revealed by in situ single-particle detection

2021 
Photostability has always been an important issue that limits the performance of organo-metal halide perovskites in optoelectronic devices. Although the photostability can be partially improved by polymer coating/encapsulation, one rising question that needs to be considered is whether the improvement of photostability is accessed at the expense of intangible loss in photoluminescence (PL) properties. By in situ analyzing the evolution of PL properties of individual perovskite crystals during the polymer encapsulation procedure, we demonstrate here that poly(methyl methacrylate), a common polymeric encapsulant, would passivate the surface defects of perovskite crystals, leading to the suppress of PL blinking. However, somewhat counterintuitive, the toluene solvent will induce the PL decline of individual perovskite crystals via accumulation of the number of quenchers that, most probably, are related to the ion migration in perovskite. The findings at the single-particle level emphasize the often-neglected role of the polymer matrix and the solvent in the optical properties of perovskite material during the polymer encapsulation process, and will guide the further design of more stable and high-performance devices based on perovskite.
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