Low-dimensional copper (I)-based ternary metal halides , having the features of nontoxicity, outstanding optical performance and great air-stability, is becoming the promising substitutes for traditional metal perovskite halides . Despite the impressive progress in copper halides, highly effective synthesis of their nanocrystals with precise shape and size control, compared to that of conventional lead halide semiconductors, is still remained to be explored. In this work, we report a systematically optimized finds for the colloidal synthesis conditions of Cs 3 Cu 2 Cl 5 nanocrystals (NCs). The Cs 3 Cu 2 Cl 5 NCs are modulated from nanoparticles to nanorods and to nanoplates by adjusting reaction temperature and reaction time. Cs 3 Cu 2 Cl 5 nanorods give a wide emission at 510 nm, being caused by self-trapped exciton state with exciton binding energy of 137 meV and phonon–electron interaction of 25 meV as determined by temperature-dependent photoluminescence spectra. The photoluminescence quantum yield (PLQY) of the nanorods that were reacted at 150 °C for 1200 s, an optimal reaction condition, reaches up to 80.19%. We also find for the first time that the optical quality of Cs 3 Cu 2 Cl 5 NCs is positively related to the full width at half maximum of main peak in X-ray diffraction pattern . The findings in this work give a view to the future planning for Cs 3 Cu 2 Cl 5 ’s colloidal synthesis and raise an intuitive criterion for the quality of as-synthesized Cs 3 Cu 2 Cl 5 NCs.
Yang Tang,Qingyu Xie,Xuanming Zhang,Jiwei Ma,Hao Xie,Yongfeng Liu,Liang Zhao,Dongdong Yan,Xiaoyu Wang,Weixiang Ye
Cs 3 Cu 2 Cl 5 nanocrystals (NCs) have emerged as promising optoelectronic materials owing to their efficient self-trapped exciton (STE) emission. However, their limited environmental stability has significantly constrained their application in light-emitting diodes (LEDs). In this work, a facile ambient-air synthesis strategy is developed for Mg 2 ⁺-doped Cs 3 Cu 2 Cl 5 NCs that simultaneously addresses both stability and emission efficiency challenges. Remarkably, optimal Mg 2 ⁺ doping (20%) enhances the photoluminescence quantum yield (PLQY) from 28.69% to 59.3%. Comprehensive theoretical investigations through density of states (DOS) calculations and ab initio molecular dynamics (AIMD) simulations demonstrate that Mg 2 ⁺ doping induces bandgap narrowing for enhanced radiative recombination while reinforcing the crystal lattice stability. When integrated with a UV LED chip, the optimized NCs enable the fabrication of high-performance green LEDs exhibiting outstanding luminance (17 281 cd m − 2 ) and excellent color stability (CIE coordinates: 0.354, 0.518). This study provides not only a practical synthetic approach for stable copper halide NCs but also valuable insights for designing efficient STE emitters for optoelectronic applications.
The poor stability of lead-free Cs 3 Cu 2 Cl 5 nanocrystals (NCs) is the main impediment for their broad practical applications. Here, a sol-gel reaction using tetraethoxysilane (TEOS) as the silica coating precursor to prepare Cs 3 Cu 2 Cl 5 @SiO x NCs is proposed. Due to the efficient passivation and robust protection of SiO x shells on the NCs surface, Cs 3 Cu 2 Cl 5 @SiO x NCs solution and films exhibit a high photoluminescence quantum yield of 98% and 76%, respectively, and improved stability against water and heat. Cs 3 Cu 2 Cl 5 @SiO x NCs are then used to fabricate warm white light-emitting diodes (WLEDs), which show a high color-rendering index of 94 and a proper correlated color temperature of 5049 K, and maintain an excellent thermal (265–360 K) and prolonged operating (380 h) stability. In addition, the good white light emission facilitates the application in visible light communication (VLC). The VLC light source demonstrates a −3 dB bandwidth of 420 kHz, and the achieved data rate of the VLC system reaches 2.65 Mbps using orthogonal frequency division multiplexing modulation with a bit loading. As a result, lead-free Cs 3 Cu 2 Cl 5 @SiO x NCs with an efficient optical performance and an excellent stability might promote the development of stable NCs and extend the applications in optoelectronics.
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