Synthesis of Chemically Stable Ultrathin SiO₂-Coated Core–Shell Perovskite QDs via Modulation of Ligand Binding Energy for All-Solution-Processed Light-Emitting Diodes

Abstract

Recently, perovskite quantum dots (QDs) have attracted intensive interest due to their outstanding optical properties, but their extremely poor chemical stability hinders the development of the high-performance perovskite QD-based light-emitting diodes (PeLEDs). In this study, chemically stable SiO2-coated core–shell perovskite QDs are prepared to fabricate all-solution-processed PeLEDs. When the SiO2 shell thickness increases, the chemical stability of perovskite QDs is dramatically improved, while the charge injection efficiency is significantly decreased, which becomes the biggest obstacle for PeLED applications. Thus, controlling the SiO2 thickness is essential to obtain core–shell perovskite QDs optimal for PeLEDs in an aspect of chemical and optoelectrical properties. The 3-aminopropyl-triethoxysilane (APTES)/oleylamine (OAm) volume ratio is found to be a critical factor for obtaining an ultrathin SiO2 shell. Optimization of the APTES/OAm ratio affords A-site-doped CsPbBr3 QDs with an ultrathin SiO2 shell (A-CsPbBr3@SiO2 QDs) that exhibit longer radiative lifetimes and smaller shallow trap fraction than those without A-site doping, resulting in a higher photoluminescence quantum yield. A-CsPbBr3@SiO2 QDs also demonstrate long-term superior chemical stability in polar solvents without loss of optical properties due to passivation by the SiO2 shell and less defects via A-site doping. Consequently, all-solution-processed PeLED is successfully fabricated under ambient conditions, facilitating perovskite QD utilization in low-cost, large-area, flexible next-generation displays.

Insulating CsPbBr3 Quantum Dots via Encapsulation with SiOx: Interfacial Electron Trafficking and Interaction beyond the Insulating Boundary

“…First, the focus was on the material/photophysical properties of core CsPbBr 3 PQDs. In this study, ethylene glycol (EG) and (3-aminopropyl)­triethoxysilane (APTES) were used as coordinating ligands and precursors, respectively, for the silica shell, using a modified ligand-assisted reprecipitation technique ,,, (see details in the Experimental Section in the Supporting Information). The ligand-assisted reprecipitation process in this study involved dissolving the perovskite precursors in N,N- dimethylformamide (DMF).…”

“…Thus, by inducing the quantum confinement effect, these perovskites exhibit unique photophysical properties such as high photoluminescence quantum yield (PLQY, >90%) via effective defect control techniques, − band gap modulation, and large surface-to-volume ratio. In particular, 0D perovskite quantum dots (PQDs) have been utilized in a variety of optoelectronic devices, such as solar cells, LEDs, photodetectors, image sensors, and memory devices . Various synthetic strategies have been applied to produce PQDs, such as hot-injection growth, , surfactant-directed solution-phase growth, and ligand-assisted precipitation. , Typically, long-carbon-chain organic ligands, such as oleic acid and oleylamine, have been used to fabricate PQDs to control the crystal size, growth rate, and surface energy stabilization, thus reducing the direct contact between the perovskites and H 2 O .…”

Enhanced Stability and Luminous Performance for Structured Mn‐Doped CsPbCl3 Quantum Dots

“…The peaks around 3000∼3100 cm −1 and 1381∼1626 cm −1 are the vibrations of the C=C bond of the toluene, the peaks around 2878∼2940 cm −1 could be attributed to the alkyl‐group (−CH 2 and −CH 3 ). The coated sample has an additional peak for the Si−O−Si bonds and Si‐OH bonds, which indicates the successful hydrolysis of APTES [39] . Furthermore, combined with the results for the 102 eV binding energy peak of the Si 2p state in Figure 2a, the silica from the hydrolysis of APTES is more credible.…”

“…The coated sample has an additional peak for the SiÀ OÀ Si bonds and Si-OH bonds, which indicates the successful hydrolysis of APTES. [39] Furthermore, combined with the results for the 102 eV binding energy peak of the Si 2p state in Figure 2a, the silica from the hydrolysis of APTES is more credible. To further verify the stability of the QDs by the combined strategies of doping and coating, the non-doped QDs, Mndoped QDs, and doped & coated QDs were dispersed in toluene and water at a ratio of 5 : 1, and the aging tests for PL spectra under this aqueous and polar solvent conditions have been systematically investigated.…”

4‐Bromo‐Butyric Acid‐Assisted In Situ Passivation Strategy for Superstable All‐Inorganic Halide Perovskite CsPbX3 Quantum Dots in Polar Media

“…[5,6] Much effort has been dedicated to the strategy for overcoming the obstacles of instability of CPX QDs. In particular, various postsynthetic surface treatment methods have been universally employed to improve the chemical stability of CsPbBr 3 (CPB) QDs by encapsulating CPB QDs with a hydrophobic layer composed of inorganic oxides or polymers such as SiO 2 , Ta 2 O 5 , [7][8][9] ZnS, [10] ZnO, [11] alumina, [12,13] TiO 2 , [14] glass matrices, [15] and polymers [16][17][18][19] on their surfaces, which effectively protect the CPB QDs from environmental induced deterioration. Nevertheless, it remains a serious challenge to coat a uniform hydrophobic and transparent shell on a single CPX QDs with a particle size smaller than 10 nm due to the ultrahigh surface dynamic energy of QDs.…”