Preparation and Fluorescence Properties of Silicon-Coated Cruciform Cspbbr3 Nanocrystals

Abstract

All-inorganic perovskite nanocrystals have attracted the public's attentions due to their excellent optoelectronic properties, such as narrow band gap, high color purity, and long carrier life, etc. However, due to their ionic characteristics, perovskite nanocrystals are difficult to cope with environmental factors, such as water, oxygen or heat, and the unsatisfactory stability of the crystal structure and optical properties hindered their further applications. Here, we proposed a two-stage heating method to synthesize cruciform CsPbBr3 nanocrystals (NCs), and then embedded in a silica matrix to enhance the fluorescence properties and the stability simultaneously. The CsPbBr3 NCs show 30.5 nm in length and 28.5 nm in width. After coating SiO2 derived from the hydrolysis of 3-aminopropyl triethoxysilane (APTES) with the molar ratio APTES/Pb of 2.0, the photoluminescent quantum yield (PLQY) of the obtained CsPbBr3@SiO2 composite increased from 65% to 87% due to the surface passivation by SiO2 shell. Moreover, the CsPbBr3@SiO2 composite retained 27% of the initial fluorescence intensity after 210 min storage in ethanol, while the uncoated NCs were almost fluorescence quenching completely. After storage in water for 24 h, the PL intensity of CsPbBr3@SiO2 composite and CsPbBr3 NCs was 43.5% and 3.6% of the initial PL intensity, respectively. Furthermore, PL intensity of the pristine CsPbBr3 NCs almost quenched at 398 K, while CsPbBr3@SiO2 composite retained 31% of the initial PL intensity. Finally, CsPbBr3@SiO2 composite phosphors were mixed with K2SiF6:Mn4+(KSF:Mn4+) phosphor and ultraviolet light curing glue, followed by packaging with blue light chips to achieve white light emitting diodes (WLED) devices. The CsPbBr3@SiO2-based WLED showed color rendering index (CRI) of 40.4 and correlated color temperature (CCT) of 5218 K, and the luminous efficiency (LE) was 35 lm/W. The gamut of the WLED encompasses 134.5% of the National Television Standards Committee (NTSC) color gamut standard, indicating that the encapsulation nanocrystals have a good application prospect in WLED.

Keywords: WLED, cruciform CsPbBr3 nanocrystals, surface coating, SiO2, storage stability, PL