Surface Ligand Engineering for CsPbBr₃ Quantum Dots Aiming at Aggregation Suppression and Amplified Spontaneous Emission Improvement

Abstract

In recent years, it has been reported that using ligands modification to passivate the surface is one reasonable approach to improve the optical properties and stability of perovskite quantum dots (QDs). However, a simple and effective way to diminish the aggregation phenomenon of perovskite QDs is still challenging. Herein, a ligand‐engineering strategy is adopted to fabricate CsPbBr3 QDs by applying a shorter capping ligand octylamine (OLA) to replace the commonly used long ligand oleylamine (OAm). After the ligand modification, the photoluminescence quantum yield of CsPbBr3 QDs is enhanced from 62.4% to 91.3%. No aggregation or degradation phenomenon can be observed in solution even after being exposed to the air for 100 days. Moreover, the OLA‐CsPbBr3 QDs film can keep 96.8% of initial photoluminescence intensity even when stored under ambient condition for 5 weeks. Furthermore, the stimulated emission performance is investigated in terms of amplified spontaneous emission (ASE), and the ASE threshold of OLA‐CsPbBr3 QDs is only 24% of the OAm‐CsPbBr3 QDs threshold, and the ASE photostability is also enhanced. All the results suggest that the OLA ligand modification is an available strategy to improve the properties of CsPbBr3 QDs and to shed light on the potential practical applications for photoelectric devices.

High Optical Gain of Solution‐Processed Mixed‐Cation CsPbBr3 Thin Films towards Enhanced Amplified Spontaneous Emission

“…[33] Especially, the low concentration of long-chain organic cations tends to adhere to the surface of 3D perovskite films with structure like ligandprotected nanocrystals, which enhances the exciton oscillation strength and optical gain. [33] Followed by the recent advancement of ASE performance improvement in CsPbBr 3 quantum dots via similar surface treatment and dimension control strategies, [17,[34][35][36][37] these achievements suggest the considerable potential of mixed-cation CsPbBr 3 perovskite in low-threshold, thermally-preferable lasing. The analysis of the stimulated emission behavior and understanding of the optical-gain dynamic of the thin films of these mixed-cation perovskites would provide solutions for reducing the lasing threshold and establishing applicable all-solution-processed lasers, all of which, however, are still inadequate.…”

Sodium doping for enhanced performance by highly efficient CsPbBr3 quantum dot-based electroluminescent light-emitting diodes

“…11,12 Even though perovskite QDs have made great progress in QLED devices, [13][14][15][16] the surface defects of perovskite QDs are still the main problem hindering their further practical application. At present, CsPbX 3 QDs are generally obtained via the hot-injection method, 17 ligand-assisted reprecipitation method, 18 ultrasonic method, 19 microwave-assisted method, 20 and template method. 21 For the purposes of large-scale fabrication and low cost, the ligand-assisted reprecipitation method is the recommended synthetic method.…”

Enhancement of Light Amplification of CsPbBr3 Perovskite Quantum Dot Films via Surface Encapsulation by PMMA Polymer

“…Thus, the ASE photostability of synthesized films is significantly improved after PMMA coating. The improved stability can be ascribed to ligands engineering (lengths of ligands-the short branched chains) of the CsPbBr 3 PQD [48,49] and also by incorporation into hydrophobic polymer matrices [45]. The short branched chains will be increase the binding energy between the ligands and QDs and the lengths of ligands, which is related to the strength of the van der Waals (VDW) interactions among the ligands, and the strength is dominant to determine the crystalline structure and follow the optical properties of PQDs [49][50][51][52].…”