Colloidal Synthesis and Tunable Multicolor Emission of Vacancy‐Ordered Cs₂HfCl₆ Perovskite Nanocrystals

Abstract

Vacancy‐ordered perovskite nanocrystals (NCs) have recently attracted much interest owing to their unique structure and optical properties; however, regulating self‐trapped excitons (STEs) in vacancy‐ordered perovskite NCs to exhibit tunable multicolor emission is still challenging because of the highly localized charge distribution and strong carrier‐phonon coupling. Herein, the first colloidal synthesis of lead‐free vacancy‐ordered Cs2HfCl6 perovskite NCs by a hot‐injection method using hafnium acetylacetonate as metal precursors is reported. The passivation strategy of sub‐bandgap trap states inside Cs2HfCl6 NCs is proposed by doping Sb3+. X‐ray photoelectron spectroscopy (XPS) measurements verify that the passivation of sub‐bandgap trap states may be attributed to the enhanced chemical interaction between the Hf4+ cations and Cl– anions. Simultaneously, the introduction of Sb3+ ions yields a bright orange emission. Employing lanthanide acetylacetonate compounds, four lanthanide ions including Pr3+, Eu3+, Tb3+, and Ho3+ are doped into the Cs2HfCl6 NCs, which achieves tunable multicolor emissions (from blue to green to pink) through the energy transfer from STEs to lanthanide ions. This investigation not only develops a novel vacancy‐ordered perovskite NCs, but also provides effective strategies for tuning the optical properties of lead‐free vacancy‐ordered perovskite NCs.

Efficiently Improved Photoluminescence in Cesium Lead Halide Perovskite Nanocrystals by Using Bis(trifluoromethane)sulfonimide

“…The use of superacid combined with a polymer for improving the photoluminescence and stability in CsPbX 3 could provide a novel alternative strategy for high-PLQY CsPbX 3 fabrication and their device applications. Moreover, the strategy of utilizing TFSI and even its analogues could also inspire the further development of lead-free perovskites and other types of nanocrystals. , …”

Red‐Emitting Perovskite Variant Cs2PtCl6 Phosphor: Material Design, Luminous Mechanism, and Application in High‐Color‐Rendering White Light‐Emitting Diodes

“…[19,20] Fortunately, the lowdimensional structure of A 2 BX 6 provides a natural quantum confinement effect, which may produce prospective luminescent properties.Recently, many A 2 BX 6 perovskite variants, mostly chlorides, have been examined as luminescence materials. [21][22][23][24] The luminescent properties of these A 2 BX 6 perovskite variants depend strongly on the tetravalent B cations. For the group IVB transition metal cations Hf 4+ and Zr 4+ , the corresponding perovskite variants Cs 2 ZrCl 6 and Cs 2 HfCl 6 have ultrawide bandgaps and exhibit broad deep-blue emissions (454 and 452 nm, respectively) originated from self-trapped excitons (STEs).…”

Boosting the Self-Trapped Exciton Emission in Cs2NaYCl6 Double Perovskite Single Crystals and Nanocrystals

“…We further synthesized the Cs 2 NaYCl 6 NCs by using a modified hot-injection method (details are provided in the Supporting Information). As shown in Figure b, the PXRD data confirms the pure double perovskite phase of Cs 2 NaYCl 6 NCs and the diffraction peaks broadened compared to the bulk SCs because of the size effect . As evidenced by the transmission electron microscopy (TEM) in Figure d–f, the NCs have a rectangular shape with an average width and length of 8.3 and 20.6 nm, respectively.…”