Thermal degradation of luminescence in inorganic perovskite CsPbBr₃ nanocrystals

The luminescence properties of inorganic perovskite CsPbBr₃ nanocrystals (NCs) with emissions of 492 and 517 nm under thermal annealing treatment were studied by temperature-dependent photoluminescence (PL) spectroscopy. The CsPbBr₃ NCs were annealed in vacuum at various temperatures. It was found that the NCs exhibited significant thermal degradation of PL at thermal annealing temperatures above 320 K. The transmission electron microscopy, X-ray diffraction and PL spectroscopy demonstrated that the size of NCs almost kept constant at thermal annealing temperatures below 360 K while it significantly enlarged at higher thermal temperatures above 380 K. The PL intensities, peak energies and linewidths of the annealed NCs, as a function of temperature, are discussed in detail. The PL degradation of the NCs was related to the formation of nonradiative recombination centers due to the loss of ligands and growth of NCs under thermal annealing.