Investigation of emission behaviour of perovskite nanocrystals using nano to microspheres of TiO2

Abstract

Organic–inorganic methylammonium lead halide perovskite nanocrystals have emerged as a promising material for optoelectronic devices. But due to the lack of long-term stability of perovskite nanocrystals, their applications have been hampered in commerciality. In this work, we demonstrate the tunability in the emission of perovskite nanocrystals with different sizes of TiO₂ from nano to microspheres. The green luminescent CH₃NH₃PbBr₃ nanocrystals were synthesized by the ligand-assisted reprecipitation (LARP) method, which produced a photoluminescent quantum yield (PLQY) of 43%. The optical properties of synthesized perovskite nanocrystals were recorded with different sizes of TiO₂. It was found that these perovskite nanocrystals (PNC) showed quenching of photoluminescence with PLQY of 32% after sonication with nano TiO₂ (n-TiO₂), due to the higher surface of n-TiO₂ that reduces the recombination rate and improve the electron transfer from PNC to n-TiO₂. The quenching phenomenon was also depicted by the study of electrochemical measurement. However, its encapsulation into the pores of TiO₂ microspheres (m-TiO₂) remarkably enhances the PLQY to 95%. Moreover, the enhancement of stability was also observed in the latter case. Furthermore, the encapsulation of perovskite nanocrystals was examined using transmission electron microscopy (TEM) and nitrogen adsorption–desorption isotherm analysis.