Efficiently Green-Emitting and Ultra-Stable CsPbBr3@SiO2 Nanocomposites for White Light-Emitting Diodes

Inorganic oxide especially SiO2 encapsulation strategy is an effective way to improve the stability of all-inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (NCs). However, when CsPbX3 NCs are encapsulated in SiO2 by in situ tetraethyl orthosilicate (TEOS) hydrolysis, the unavoidable by-products (water and ethanol) of TEOS hydrolysis commonly damage the structural and optical properties of the CsPbX3 NCs. Herein, TDPA-CsPbBr3 NCs with the dense tetradecylphosphonic acid (TDPA) passivation were pre-prepared and subsequently encapsulated into SiO2 via in situ TEOS hydrolysis. Benefitting from the dense phosphonic passivation layer capable of resisting the erosion of polar by-products generated by TEOS hydrolysis, the obtained TDPA-CsPbBr3@SiO2 nanocomposites maintain the excellent optical properties of the colloidal CsPbBr3 NCs, showing near-unity photoluminescence quantum yield (PLQY) and ultra-narrow full width at half maximum (FWHM). Furthermore, the TDPA-CsPbBr3@SiO2 nanocomposites exhibit outstanding stability against ethanol, UV light, and heating treatment due to the dual protection of dense phosphonate ligand layers and inorganic SiO2 matrix. The white light-emitting diodes (WLED) device was fabricated by sequentially depositing green-emitting TDPA-CsPbBr3@SiO2 nanocomposites and red-emitting K2SiF6:Mn on blue-emitting GaN LED chip. The obtained WLED exhibits excellent luminous performances with standard white emission of CIE Coordinates (0.33, 0.33), a color gamut 138 % of the NTSC and 103 % of Rec. 2020, respectively. This study demonstrates that TDPA-CsPbBr3@SiO2 nanocomposites have a potential application in solid-state lighting and backlight displays.