Stokes shift engineered, stable core-shell perovskite nanoparticle - Poly (methyl methacrylate) composites with high photoluminescence quantum yield

摘要

Organometallic lead halide perovskites are well known for its excellent and unique light-harvesting properties. This brands them as a promising candidate in almost all the optoelectronic devices. Present work demonstrates the synthesis of methylammonium lead bromide, MAPbBr(3) quantum dots (QDs) of diameter less than 4 nm and methylammonium - octylammonium lead bromide core-shell type nanoparticles (CSNPs) with a core diameter of about 1-2 nm surrounded by a shell of thickness 4 nm. The core-shell structure was confirmed from crystal structure analysis X-ray diffraction pattern, transmission electron microscopy (TEM) images and an increased stokes shift between absorption edge and the photoluminescence emission peak. These core-shell nanoparticles with high photoluminescence quantum yield (PLQY) and color tuning ability were incorporated into poly(methyl methacrylate) (PMMA) matrix to form transparent nanocomposites which were highly stable, with reduced wettability and a high PLQY of 88%. PLQY stability of composites towards humidity was examined by keeping the samples fully immersed in water for 18 h, after which PMMA composites were showing PLQY similar to 83%, no considerable difference was found compared to dry composites. Dry films (kept sealed in covers) were found to be relatively stable for about one year retaining PLQY of 13%. The composite films of core-shell particles were used to demonstrate a prototype of down converting light emitting diode (LED), emitting pure green light capable of improving the quality of display devices.