Chen Zhang,Zeyu Wang,Zheyuan Da,Jindou Shi,Junnan Wang,Youlong Xu,Nikolai V. Gaponenko,Arshad Saleem Bhatti,Minqiang Wang
The core–shell structure is an effective means to improve the stability and optoelectronic properties of cesium lead halide (CsPbX3 (X = Cl, Br, I)) perovskite quantum dots (QDs). However, confined by the ionic radius differences, developing a core–shell packaging strategy suitable for the entire CsPbX3 system remains a challenge. In this study, we introduce an optimized hot-injection method for the epitaxial growth of the CsPb2X5 substrate on CsPbX3 surfaces, achieved by precisely controlling the reaction time and the ratio of lead halide precursors. The synthesized CsPbX3/CsPb2X5 composite microplates exhibit an emission light spectrum that covers the entire visible range. Crystallographic analyses and density functional theory (DFT) calculations reveal a minimal lattice mismatch between the (002) plane of CsPb2X5 and the (1ˉ10) plane of CsPbX3, facilitating the formation of high-quality type-I heterojunctions. Furthermore, introducing Cl– and I– significantly alters the surface energy of CsPb2X5’s (110) plane, leading to an evolutionary morphological shift of grains from circular to square microplates. Benefiting from the passivation of CsPb2X5, the composites exhibit enhanced optical properties and stability. Subsequently, the white light-emitting diode prepared using the CsPbX3/CsPb2X5 composite microplates has a high luminescence efficiency of 136.76 lm/W and the PL intensity decays by only 3.6% after 24 h of continuous operation.
Highly crystalline CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) are in situ grown in silicalite-1 zeolite framework by a high-temperature solid-state reaction at 600 °C without ligand addition. Subsequently, a CsPb 2 X 5 shell is hetero-epitaxial grown to form a CsPbX 3 /CsPb 2 X 5 core–shell structure. The resulting nanocomposites exhibit high photoluminescence quantum yields (PLQYs) and remarkable stability in a solid powder situation. The green-emitting (Br-based) and red-emitting (I-based) composites demonstrate nearly identical high PLQYs up to 82.9 and 83.2%, respectively, due to high crystallinity and core–shell structure. By easily adjusting halide compositions, the photoluminescence peak wavelengths of the NCs can be continuously tuned in the whole visible spectrum from 413 to 697 nm. These nanocomposites exhibit remarkable resistance to both photo-degradation under UV light irradiation and hydrolytic degradation in humid environments due to a hydrothermal treatment. The superior optoelectronic performance is ascribed to heterostructure formation and the protective confinement provided by the mesoporous silicalite-1 framework, which effectively passivates surface defects. Finally, the NCs are successfully applied to white light-emitting devices, achieving a chromaticity coordinate of (0.33, 0.32) and a correlated color temperature of 4793 K. This dual-passivation strategy, combining zeolite encapsulation and surface reconstruction, renders the nanocomposites particularly suitable for implementation in next-generation display technologies.
Compositionally related cesium lead halide materials, such as CsPb2X5, have attracted great interest due to their considerable optoelectronic/optical properties as well as improved stability. Currently, CsPb2Br5 nanocrystals can be well-designed by tuning the ligands or precursor ratio, whereas, CsPb2X5 (with Cl− or I−) nanocrystals can only be obtained by the anion exchange method. Herein, we report a method to directly synthesize CsPb2X5 facilitated by thiol ligands. The morphology of CsPb2X5 can be designed as a nanowire. Importantly, the stability of directly synthesized CsPb2X5 nanowires is much improved when compared with the stabilities of the materials obtained by the anion-exchange method. We believe that this method will promote the application of 1D tetragonal CsPb2X5 in optoelectronics, optics and other fields.
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