Stable CsPbBr₃:Sn@SiO₂ and Cs₄PbBr₆:Sn@SiO₂ Core–Shell Quantum Dots with Tunable Color Emission for Light-Emitting Diodes

Abstract

CsPbBr 3 perovskite quantum dots (QDs) have attracted great attention due to their different photoluminescent and electronic properties. However, the toxicity and low stability hinder their practical application. Here, low-toxicity Sn-substituted cesium lead bromide perovskite QDs were synthesized via the room temperature crystallization method. A phase transition of the perovskite quantum dots with the concentration of Sn increasing was found: the crystal phase of CsPbBr 3 :Sn perovskite QDs starts to be transformed into Cs 4 PbBr 6 :Sn perovskite QDs when the SnBr 2 precursor exceeds 30 at. %. In this process, the controlled-color emission of perovskite QDs from green to blue can be realized. To improve the stability of quantum dots, CsPbBr 3 :Sn@SiO 2 and Cs 4 PbBr 6 :Sn@SiO 2 were synthesized via a simple one-step synthesis with hydrolysis of tetramethoxysilane in toluene solution containing perovskite QDs. The results show that CsPbBr 3 :Sn@SiO 2 and Cs 4 PbBr 6 :Sn@SiO 2 exhibited higher water stability and water solubility than pure QDs. In a mixed solution of toluene and water, the PL intensity of the CsPbBr 3 :Sn@SiO 2 retained 46.7% and the Cs 4 PbBr 6 :Sn@SiO 2 was 59.6% even after 24 h of reaction compared with the initial intensities. These quantum dots with good stability and luminescent property developed in this work are expected to be widely used in light-emitting diodes.

Core/Shell Metal Halide Perovskite Nanocrystals for Optoelectronic Applications

“…The decreased PL intensity of CsPbBr 3 /SiO 2 was partially attributed to the decomposition of the core CsPbBr 3 NCs by alcohol molecules during the hydrolysis and polymerization of APTES and the effect of water. [ 113 ] Similarly, enhanced water tolerance was reported for CsPbBr 3 /SiO 2 [ 38,79,108,110,112,115 ] and CsPbBr 3 : Sn/SiO 2 [ 114 ] compared with core only NCs. For the NCs with silica shell, the long soaking and stirring in water could lead to an increase of their size and gradual transformation to nanoplates, due to replacement of the surfactant (OA, OLA, TOPO, etc.)…”

“…The SiO 2 growth on perovskite NCs can be achieved by a direct hydrolysis method using tetraethyl orthosilicate (TEOS) as precursor. [ 79,114 ] However, the presence of H 2 O is detrimental to the properties of perovskite NCs. Tang et al.…”

“…[ 79,80,85 ] The perovskite/SiO 2 core/shell NCs have been widely studied for such applications, as SiO 2 can improve perovskite stability and PLQY, and provides an optically transparent, chemically inert, and non‐toxic shell. [ 39,79,80,83,85,110,112,114,115,139,166 ] Sun et al. [ 80 ] fabricated white LEDs (WLEDs) using a NCs/SiO 2 layer containing green CsPbBr 3 and red CsPb(Br/I) 3 perovskites deposited on blue‐LEDs.…”

“…Oxides such as silica (SiO 2 ), [38,75,79,[108][109][110][111][112][113][114][115][116] titanium oxide (TiO 2 ), [49,117] alumina (Al 2 O 3 ) [118] and zirconium oxide (ZrO 2 ) [51,81] have been successfully used as the shell materials for the coreshell structured perovskite NCs to improve their mechanical rigidity and chemical stability. Although SiO 2 has been shown to improve photostability of semiconductor NCs, this is not achieved in perovskites due to their strong ionic nature.…”

“…The SiO 2 growth on perovskite NCs can be achieved by a direct hydrolysis method using tetraethyl orthosilicate (TEOS) as precursor. [79,114] However, the presence of H 2 O is detrimental to the properties of perovskite NCs. Tang et al [79] introduced a multibranched TOPO capping ligand to reduce the interaction between the CsPbMnX 3 NCs and the water molecules, while 2-methoxyethanol (2-ME) was used as a catalyst to promote [77] Copyright 2019, Wiley-VCH.…”