High-Efficiency Violet-Emitting All-Inorganic Perovskite Nanocrystals Enabled by Alkaline-Earth Metal Passivation

Abstract

Cesium lead halide perovskite nanocrystals (NCs) have emerged as promising luminescent materials for a range of applications. However, the creation of highly luminescent violet-emitting CsPbCl3 NCs mostly relies on doping of a limited number of small-sized metal ions or post-synthetic surface treatment of NCs. Alkaline-earth (AE) metals (e.g., Ca2+, Sr2+, and Ba2+) have been proposed to be able to substitute Pb2+ in halide perovskites, yet it remains incompletely understood whether AE metal ions can be incorporated into the perovskite lattice or can be merely situated at the surface. Here, we explore the possibility of using AE metal ions for the suppression of the formation of trap centers, which leads us to develop a one-pot synthetic passivation strategy to boost the violet-emitting efficiency of CsPbCl3 NCs through the creation of a Ca2+/Sr2+ involved passivation layer. The photoluminescence quantum yield of violet emission reaches 77.1% by incorporating an optimal amount of Ca2+. A wide range of optical and structural characterizations, coupled with first-principles calculations, aid in clarifying the underlying mechanism for the AE-metal-dependent passivation of CsPbCl3 NCs. Specifically, based on the experimental and theoretical results, a model is proposed for the observed abnormal incorporation phenomenon of AE2+ ions in NCs (i.e., Ba2+ can be incorporated into the core of NCs, Ca2+/Sr2+ can only be at/near the surface, while Mg2+ can neither be in the core nor at the surface). We believe that the knowledge gained here may not only offer a new perspective to obtain high-efficiency violet-emitting perovskite NCs through a one-pot synthetic passivation but can also help elucidate the functions that AE2+ ions play in the optimization of perovskite optoelectronic devices.

Mn2+/Yb3+ Codoped CsPbCl3 Perovskite Nanocrystals with Triple‐Wavelength Emission for Luminescent Solar Concentrators

“…demonstrated including main group elements (e.g., Al, Ca, Sr, Bi), [7][8][9][10] transition metals (e.g., Mn, Ni, Cd), [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and rare earth elements (e.g., Yb, Ce, Pr). [26][27][28][29][30][31][32][33][34][35][36][37] Among all the dopant-induced properties, the emergence of new emission bands due to the introduction of additional radiative relaxation channels of excitons has been intriguing and promising in particular.…”

Nano Ball‐Milling Using Titania Nanoparticles to Anchor Cesium Lead Bromine Nanocrystals and Energy Transfer Characteristics in TiO2@CsPbBr3 Architecture

“…Without addition of TiO 2 NPs, there is cubic contour for CsPbBr 3 NCs with an average size of 13.3 nm (Figure S1, Supporting Information), which is larger than that of NCs synthesized by hot‐injection method due to its relatively long reaction time. [ 22–28 ] It indicates that the grinding is an efficient method to synthesize CsPbBr 3 NCs with cubic morphology, which can also be achieved by ball‐milling methods as reported in the previous works. [ 13,14 ] Meanwhile, there are the distinct lattice fringes as shown in Figure 1b, which indicates the nanomaterials can also crystallize well at room temperature.…”

Inhibition of Phase Segregation in Cesium Lead Mixed-Halide Perovskites by B-Site Doping

“…Therefore, B-site doping with Mn 2+ ions should be a promising way to inhibit the light-induced phase segregation of mixed-halide perovskite materials and can simultaneously improve the stability in ambient atmosphere. In addition, other divalent cations including Zn 2+ , Cd 2+ , and alkaline-earth metals are reported to have been successfully incorporated into CsPbX 3 nanocrystals ( Cai et al., 2018 ; Chen et al., 2019 ; van der Stam et al., 2017 ). We believe that the doping of these ions will also affect the stability of the materials.…”