CsPb(Br/Cl)3 Perovskite Nanocrystals with Bright Blue Emission Synergistically Modified by Calcium Halide and Ammonium Ion

Bifunctional Ligand Passivation Enables Stable Blue Mixed-Halide CsPb(Br/Cl)3 Perovskite Quantum Dots toward Light-Emitting Diodes

Mixed-halide CsPb(Br/Cl)3 perovskite quantum dots (PeQDs) have attracted extensive attention in light-emitting diodes (LEDs), but their low photoluminescent efficiency and especially poor stability impede their practical applications. Here, we employ bifunctional didodecyldimethylammonium thiocyanide (DDASCN) with a pseudohalogen SCN- and branched DDA+ to obtain blue-emitting CsPbBr2Cl PeQDs. DDASCN significantly boosts the photoluminescence quantum yield to 92% by inhibiting nonradiative recombination. Importantly, DDASCN PeQDs show excellent stabilities against air, UV light, heat, and polar solvents. These improved performances were explained by density functional theory calculation, which shows that SCN- fills the Cl- vacancy by simultaneously binding with undercoordinated Pb2+ and Cs+, while DDA+ connects undercoordinated Br- and lies parallel to the PeQD core, leading to efficient passivation and a strong binding capacity. Finally, we achieved high-performance white LEDs by integrating our PeQDs, resulting in a color-rendering index of 92.9, a color gamut of 119.61%, and chromaticity coordinates of (0.33, 0.33). This provides an effective method to obtain efficient and stable CsPb(Br/Cl)3 PeQDs for practical applications.

Enhancing Photoluminescence of CsPb(ClxBr1-x)3 Perovskite Nanocrystals by Fe2+ Doping

The doping of impurity ions into perovskite lattices has been scrupulously developed as a promising method to stabilize the crystallographic structure and modulate the optoelectronic properties. However, the photoluminescence (PL) of Fe²⁺-doped mixed halide perovskite NCs is still relatively unexplored. In this work, the Fe²⁺-doped CsPb(Cl_xBr_1-x)₃ nanocrystals (NCs) are prepared by a hot injection method. In addition, their optical absorption, photoluminescence (PL), PL lifetimes, and photostabilities are compared with those of undoped CsPb(Br_1-xCl_x)₃ NCs. We find the Fe²⁺ doping results in the redshift of the absorption edge and PL. Moreover, the full width at half maximums (FWHMs) are decreased, PL quantum yields (QYs) are improved, and PL lifetimes are extended, suggesting the defect density is reduced by the Fe²⁺ doping. Moreover, the photostability is significantly improved after the Fe²⁺ doping. Therefore, this work reveals that Fe²⁺ doping is a very promising approach to modulate the optical properties of mixed halide perovskite NCs.

Optimizing the Synthetic Conditions of "Green" Colloidal AgBiS2 Nanocrystals Using a Low-Cost Sulfur Source

Colloidal AgBiS₂ nanocrystals (NCs) have attracted increasing attention as a near-infrared absorbent materials with non-toxic elements and a high absorption coefficient. In recent years, colloidal AgBiS₂ NCs have typically been synthesized via the hot injection method using hexamethyldisilathiane (TMS) as the sulfur source. However, the cost of TMS is one of the biggest obstacles to large-scale synthesis of colloidal AgBiS₂ NCs. Herein, we synthesized colloidal AgBiS₂ NCs using oleylamine@sulfur (OLA-S) solution as the sulfur source instead of TMS and optimized the synthesis conditions of colloidal AgBiS₂ NCs. By controlling the reaction injection temperature and the dosage of OLA-S, colloidal AgBiS₂ NCs with adjustable size can be synthesized. Compared with TMS-based colloidal AgBiS₂ NCs, the colloidal AgBiS₂ NCs based on OLA-S has good crystallinity and fewer defects.