Wenbin Shi,Xiao Zhang,Cong Xie,Hsueh Shih Chen,Ping Yang
To overcome the poor stability of metal halide perovskite nanocrystals (NCs) prepared in organic solvents, a solid reaction method at high temperature was developed using sol–gel porous SiO 2 as a reactor. Sol-gel SiO 2 powders were used to encapsulate CsPbX 3 NCs at high temperatures (600–800 °C) in air to get SiO 2 /CsPbX 3 glass by dispersing growth cites in advance and no ligands added. After NaOH etching, a thin dense SiO 2 shell was remained on the surface of CsPbX 3 NCs (named as CsPbX 3 @SiO 2 ).The photoluminescence (PL) quantum yield of the CsPbX 3 @SiO 2 was 86.7 %, in which their PL peak wavelengths were adjusted from 410-707 nm by changing halogen components. The dense SiO 2 shell on CsPbX 3 NCs blocked the connection of CsPbX 3 cores with water and oxygen in the external environment, resulting in CsPbX 3 @SiO 2 revealed extraordinary high stability. After immersing in water for half year, the PL intensity of CsPbX 3 @SiO 2 composites was remained unchanged and the composites still revealed bright PL after heat-treating in boiling water for 14 h. These highly stable composites were used to fabricate a white light-emitting diode, in which the color coordinates are located at (0.36, 0.33), and the color temperature reaches 5169 K which belongs to the warm white light range.
The optoelectronic effects of sidewall passivation on micro-light-emitting diodes (Micro-LEDs) were investigated using sol-gel chemical synthesis. Blue InGaN/GaN multi-quantum well (MQW) Micro-LEDs, ranging in size from 20 × 20 μm to 100 × 100 μm and with high EQE, were fabricated and distinguished by the passivation method used, including no passivation, sol-gel SiO2, and plasma-enhanced chemical vapor deposition (PECVD) SiO2. Impressively, the sol-gel method is advantageous in improving the optoelectronic performance of Micro-LEDs. The fabricated 20 × 20 μm Micro-LEDs showed an EQE of 27.7% with sol-gel passivation, which was a 14% improvement compared to devices without sidewall passivation. Sol-gel sidewall passivation allows Micro-LEDs to effectively achieve sharper edge emission, superior surface luminous uniformity, and intensity, providing the possibility for the fabrication of low-cost and high-efficiency Micro-LEDs.Keywords:sidewall passivation;sol-gel SiO2;GaN-based micro-light-emitting diodes (Micro-LEDs)
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