Thermal degradation of luminescence in inorganic perovskite CsPbBr₃nanocrystals

Abstract

The luminescence properties of inorganic perovskite CsPbBr nanocrystals (NCs) with emissions of 492 and 517 nm under thermal annealing treatment were studied by temperature-dependent photoluminescence (PL) spectroscopy. The CsPbBr 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.

Quantifying the Thermodynamics of Ligand Binding to CsPbBr3 Quantum Dots

“…In summary,w eh ave studied the surface chemistry of CsPbBr 3 QDs capped with oleic acid and oleylamine native ligands.L igand exchange reactions for carboxylic acids, amines,a nd phosphonic acids were performed on CsPbBr 3 QDs.B yu sing 1 HNMR spectroscopy,w ed etermined thermodynamic parameters for carboxylic acid and amine exchange with the native ligands,a nd it was determined that both reactions are in dynamic equilibrium. In contrast, phosphonic acid irreversibly exchanges the native oleate ligands,r esulting in tightly bound phosphonate.T he quantitative investigation of ligand exchange parameters by NMR methods gives needed insight into the surface chemistry of CsPbBr 3 QDs,providing abetter understanding of the effects of carboxylic acids,a mines,a nd phosphonic acids on the optoelectronic properties of these QDs.I ndeed, consistent with prior empirical observations, [16,17] we have demonstrated that more strongly bound conjugate base ligands correlate with increases in steady-state PL intensity.T his may be ar esult of the stronger binding of these ligands in this ionic system (with ahigher on/off ratio), better passivating surface defects and reducing surface-trap-assisted quenching. [18] It is expected that this method can be utilized to study ligand binding for other lead halide perovskite QDs,w ith varying Asite cations and Xsite anions,inf uture studies.…”

“…The quantitative investigation of ligand exchange parameters via NMR methods gives needed insight into the surface chemistry of CsPbBr 3 QDs, allowing for better understanding of the effects of carboxylic acids, amines, and phosphonic acids on the optoelectronic properties of these QDs. Indeed, consistent with prior empirical observations, [16,17] we have demonstrated that more strongly bound conjugate base ligands correlate with increases in steady-state PL intensity. This may be a result of the more strongly bound ligands in this ionic system (with a higher on:off ratio) better passivating surface defects and reducing surface-trap-assisted quenching.…”

Enhanced Thermal Stability of Halide Perovskite CsPbX3 Nanocrystals by a Facile TPU Encapsulation

“…The weak PL peak red shift phenomenon results from the relatively small grain size of the CsPbBr 3 QDs entering Cs 4 PbBr 6 NCs. Small Stokes shifts were observed in both samples, suggesting that the sample green emissions may stem from the exciton recombination by radiation at room temperature to release photons …”

“…In recent years, colloidal CsPbX 3 (X = Br, I, Cl) perovskite nanocrystals (NCs) have become a class of high‐profile star materials due to their high photoluminescence (PL) quantum yields, tunable emission wavelength, and narrow band width . However, the applications of CsPbX 3 (X = Br, I, Cl) NCs have been severely hindered by the issue of the stability, mainly derived from thermal degradation and atmospheric moisture . To address this issue, various encapsulation strategies have been proposed to protect perovskite NCs from decomposition in practical applications .…”

Ligand‐Exchange of Low‐Temperature Synthesized CsPbBr3 Perovskite toward High‐Efficiency Light‐Emitting Diodes

“…The out‐of‐plane profiles are shown in Figure S5 in the Supporting Information. As the annealing temperature increases, the diffraction peaks of the (100) plane become sharp and strong, suggesting the growth of CsPbBr 3 crystals . For CsPbBr 3 NCs anchored with OA/OLA and CA/OLA ligand pairs, the (110) peak almost disappeared (except at the position of 47° away from the substrate plane) upon heat treatment at 150 °C.…”