The high‐profile candidacy of low‐dimensional metal‐halide single crystals as promising light emitters originates from the intriguing emission properties (e.g., extremely broad luminescence spectra, ...large Stokes shift, high color rendition), which have enabled the recent great achievements on their application in lighting, artificial illumination, and scintillators. Among the family of low‐dimensional metal‐halide single crystals, zero‐dimensional (0D) materials have been featured in the lowest dimensionality, and as a consequence, strongest quantum confinement, softest lattice, and strongest electron–phonon coupling have been further translated into near‐unity photoluminescence (PL) efficiency with broadband emission. However, as far as it is known, 0D structures are significantly underexplored. Herein, an overview is provided on recent advances of 0D metal‐halide single crystals, with a focus on comprehensive understanding and insightful perspectives behind the photophysical mechanism. Additionally, the challenges and future opportunities currently faced by 0D bulk metal halides are discussed in order to provide a roadmap for the future development of novel materials with versatile optical properties suited for practical applications.
Zero‐dimensional metal halide single crystals have been featured with the lowest dimensionality and, as a consequence, strongest quantum confinement, softest lattice, and strongest electron–phonon coupling, which have been further translated into near‐unity photoluminescence (PL) efficiency, making them potential candidates in optoelectronic applications. This review aids in developing novel materials with versatile optical properties suited for practical applications.
Lead halide perovskite nanocrystals (NCs) have demonstrated great potential as appealing candidates for advanced optoelectronic applications. However, the toxicity of lead and the intrinsic ...instability toward moisture hinder their mass production and commercialization. Herein, to solve such thorny problems, novel lead‐free Cs2AgBiBr6 double perovskite NCs fabricated via a simple hot‐injection method are reported, which exhibit impressive stability in moisture, light, and temperature. Such materials are then applied into photocatalytic CO2 reduction, achieving a total electron consumption of 105 µmol g−1 under AM 1.5G illumination for 6 h. This study offers a reliable avenue for Cs2AgBiBr6 perovskite nanocrystals preparation, which holds a great potential in the further photochemical applications.
Stable lead‐free Cs2AgBiBr6 double perovskite nanocrystals with a cubic shape and an average size of 9.5 nm are successfully synthesized via the hot‐injection route, and are employed as photocatalysts to convert CO2 into solar fuels (CO and CH4). This work offers a reliable avenue for Cs2AgBiBr6 perovskite nanocrystals preparation, which holds a great potential in the further photochemical applications.
Multiple‐cation lead mixed‐halide perovskites (MLMPs) have been recognized as ideal candidates in perovskite solar cells in terms of high efficiency and stability due to decreased open‐circuit ...voltage loss and suppressed yellow phase formation. However, they still suffer from an unsatisfactory long‐term moisture stability. In this study, phosphorus‐containing Lewis acid and base molecules are employed to improve device efficiency and stability based on their multifunction including recombination reduction, phase segregation suppression, and moisture resistance. The strong fluorine‐containing Lewis acid treatment can achieve a champion PCE of 22.02%. Unencapsulated and encapsulated devices retain 63% and 80% of the initial efficiency after 14 days of aging under 75% and 85% relative humidity, respectively. The better passivation of Lewis acid implies more halide defects than Pb defects at the MLMP surface. This unbalanced defect type results from phase segregation that is the synergistic effect of Cs and halide ion migrations. Identifying defect type based on different passivation effects is beneficial to not only choose suitable passivators to boost the efficiency and slow down the moisture degradation of MLMP solar cells, but also to understand the mechanism of defect‐assisted moisture degradation.
A strong fluorine‐containing Lewis acid tris(pentafluorophenyl) phosphine (TPFP) is developed to passivate mixed perovskite solar cells, achieving a champion efficiency of 22.02% and a high stability under 85% relative humidity. The moisture degradation mechanism is phase segregation of I‐rich black phase and Cs/Br‐rich yellow phase resulting from water‐assisted synergistic Cs and halide ion migrations.
Heterojunction engineering, especially 2D/2D heterojunctions, is regarded as a quite promising strategy to manipulate the photocatalytic performance of semiconductor catalysts. In this manuscript, a ...direct Z‐scheme 2D/2D heterojunction of CsPbBr3/Bi2WO6 is designed and fabricated by a simple electrostatic self‐assembly process. By using ultrathin nanosheets with several atomic layers as the building blocks, a close CsPbBr3/Bi2WO6 heterointerface over large area with quite a short charge transport distance is obtained, which enables a valid Z‐scheme interfacial charge transfer between Bi2WO6 and CsPbBr3 and thus boosts charge separation. The CsPbBr3/Bi2WO6 heterojunction exhibits a superior photocatalytic performance toward CO2 reduction. By incorporating Pt nanoparticles as the cocatalyst, a high photoelectron consumption rate of 324.0 µmol g−1 h−1 under AM 1.5G irradiation (150 mW cm−2) is obtained, which is 12.2 fold higher than that of CsPbBr3 nanosheets. Moreover, a stable product yield of up to 1582.0 µmol g−1 and electron consumption yield of 8603.0 µmol g−1 for photocatalytic CO2 reduction to CO (11.4%) and CH4 (84.3%) can be achieved after 30 h of continuous catalytic reaction. The accelerated photogenerated charge transfer and spatial charge separation are investigated in detail by ultrafast spectra, photoelectrochemical test, and Kelvin probe force microscopy.
A Z‐Scheme 2D/2D heterojunction of CsPbBr3/Bi2WO6 is fabricated using a simple electrostatic assembly process. The as‐formed heterojunction possesses a large interface contact area and quite a short charge transport distance, which enable efficient Z‐scheme charge transfer and separation between Bi2WO6 and CsPbBr3, as well as remarkably enhanced performance toward photocatalytic CO2 reduction.
Low‐dimensional lead halide perovskite materials recently have drawn much attention owing to the intriguing broadband emissions; however, the toxicity of lead will hinder their future development. ...Now, a lead‐free (C4H14N2)2In2Br10 single crystal with a unique zero‐dimensional (0D) structure constituted by InBr63− octahedral and InBr4− tetrahedral units is described. The single crystal exhibits broadband photoluminescence (PL) that spans almost the whole visible spectrum with a lifetime of 3.2 μs. Computational and experimental studies unveil that an excited‐state structural distortion in InBr63− octahedral units enables the formation of intrinsic self‐trapped excitons (STEs) and thus contributing the broad emission. Furthermore, femtosecond transient absorption (fs‐TA) measurement reveals that the ultrafast STEs formation together with an efficient intersystem crossing has made a significant contribution to the long‐lived and broad STE‐based emission behavior.
A lead‐free indium‐based (C4H14N2)2In2Br10 single crystal was synthesized and characterized; it has a unique 0D crystal structure. An intrinsic self‐trapped exciton‐based ultra‐broad photoluminescence has been observed as a result of an excited‐state structural distortion in InBr63− octahedrons.
Glass is a group of materials with appealing qualities, including simplicity in fabrication, durability, and high transparency, and they play a crucial role in the optics field. In this paper, a new ...organic–inorganic metal halide luminescent glass exhibiting >78 % transmittance at 506–800 nm range together with a high photoluminescence quantum yield (PLQY) of 28.5 % is reported through a low‐temperature melt‐quenching approach of pre‐synthesized (HTPP)2MnBr4 (HTPP=hexyltriphenylphosphonium) single crystal. Temperature‐dependent X‐ray diffraction, polarizing microscopy, and molecular dynamics simulations were combined to investigate the glass‐crystal interconversion process, revealing the disordered nature of the glassy state. Benefiting from the transparent nature, (HTPP)2MnBr4 glass yields an outstanding spatial resolution of 10 lp mm−1 for X‐ray imaging. The superb optical properties and facility of large‐scale fabrication distinguish the organic–inorganic metal halide glass as a highly promising class of materials for optical devices.
A novel zero‐dimensional manganese‐based metal halide capable of forming a stable melt is reported. Large‐area luminescent metal halide glasses can be conveniently synthesized by the melt‐quenching method and used as scintillators for radiation detection.
Low‐dimensional luminescent lead halide perovskites have attracted tremendous attention for their fascinating optoelectronic properties, while the toxicity of lead is still considered a drawback. ...Herein, we report a novel lead‐free zero‐dimensional (0D) indium‐based perovskite (Cs2InBr5⋅H2O) single crystal that is red‐luminescent with a high photoluminescence quantum yield (PLQY) of 33 %. Experimental and computational studies reveal that the strong PL emission might originate from self‐trapping excitons (STEs) that result from an excited‐state structural deformation. More importantly, the in situ transformation between hydrated Cs2InBr5⋅H2O and the dehydrated form is accompanied with a switchable dual emission, which enables it to act as a PL water‐sensor in humidity detection or the detection of traces of water in organic solvents.
Unleaded and unleashed: A highly emissive lead‐free indium‐based perovskite single crystal, Cs2InBr5⋅H2O, was successfully prepared. The versatile material is the first reversible metal halide perovskite photoluminescence water sensor and paves the way for the application of metal halide perovskites in water detection.
Hybrid organic–inorganic lead halide perovskite single crystal thin film (SCTF) recently has attracted enormous interest in the field of optoelectronic devices, since it efficiently resolves the ...trade‐off between thickness and carrier diffusion length. However, the toxicity of lead element and the instability induced by organic component still hinder its future developments. In this work, lead‐free all‐inorganic Cs3Bi2I9 SCTF with a high orientation along (00h) has been in situ grown on indium tin oxide (ITO) glass via a space‐limited solvent evaporation crystallization method. The trap density of Cs3Bi2I9 SCTF (5.7 × 1012 cm−3) is 263 folds lower than that of the polycrystalline thin film (PCTF) counterpart, together with a 5‐order‐of‐magnitude higher carrier mobility. These superior charge transfer properties enable a photoresponse on–off ratio as high as 11 000, which far surpasses that of the PCTF device by 460 folds, comparable to the lead halide perovskite. Furthermore, the Cs3Bi2I9 SCTF photodetector exhibits outstanding stability even without any encapsulation, whose initial performance is well maintained after aging 1000 h in humid air of 50% RH or continuous on–off light illumination for 20 h. This work will pave the way to produce new families of high‐performance, stable, and nontoxic perovskite SCTF for future optoelectronic applications.
High‐quality Cs3Bi2I9 single crystal thin film (SCTF) with ≈1 µm in thickness and 4 mm in lateral size is grown via a space‐limited solvent evaporation crystallization method. The Cs3Bi2I9 SCTF–based photodetectors exhibit superior photodetecting performance such as a high on–off ratio of 104, low dark current, wide linear dynamic range, and fast response speed.
Though fluorescence‐tag‐based anti‐counterfeiting technology has distinguished itself with cost‐effective features and huge information loading capacity, the clonable decryption process of ...spatial‐resolved anti‐counterfeiting cannot meet the requirements for high‐security‐level anti‐counterfeiting. Herein, we demonstrate a spatial‐time‐dual‐resolved anti‐counterfeiting system based on new organic–inorganic hybrid halides BAPPZn2(ClyBr1−y)8 (BAPP=1,4‐bis(3‐ammoniopropyl)piperazinium, y=0–1) with ultra‐long room‐temperature phosphorescence (RTP). Remarkably, the afterglow lifetime can be facilely tuned by regulating the halide‐induced heavy‐atom effect and can be identified by the naked eyes or with the help of a simple machine vision system. Therefore, the short‐lived unicolor fluorescence and lasting‐time‐tunable RTP provide the prerequisites for unicolor‐time‐resolved anti‐counterfeiting, which lowers the decryption‐device requirements and further provides the design strategy of advanced portable anti‐counterfeiting technology.
A new zero‐dimensional Zn‐based metal halide with ultra‐long room‐temperature phosphorescence (RTP) is reported. The RTP lifetimes can be facilely regulated via halide engineering, paving the way for designing spatial‐time‐dual‐resolved anti‐counterfeiting materials.
All‐inorganic bismuth‐halide perovskites are promising alternatives for lead halide perovskites due to their admirable chemical stability and optoelectronic properties; however, these materials ...deliver inferior photoluminescence (PL) properties, severely hindering their prospects in lighting applications. Here, a novel air‐stable but non‐emissive perovskite Rb3BiCl6 is synthesized, and the material is used as a prototype to uncover origin of the poor optical performance in bismuth‐halide perovskite. It is found that the extremely strong exciton–phonon interactions with a large coupling constant up to 693 meV leads to the seriously nonradiative recombination, which, however, can be effectively suppressed to 347 meV by introducing Sb3+ ions. As a result, Sb3+‐doped Rb3BiCl6 exhibits a stable yellow emission with unprecedented PL quantum yield up to 33.6% from self‐trapped excitons. Systematic spectroscopic characterizations and theoretical calculations are carried out to unveil the intriguing photophysical mechanisms. This work reveals the effect of exciton–phonon interaction, that is often underemphasized, on a material's photophysical properties.
All‐inorganic lead‐free bismuth‐halide perovskite with excellent structural stability shows inferior photoluminescence performance due to the extremely strong exciton–phonon interaction, which however can be effectively suppressed by an ion doping strategy. This work provides a new avenue for the development of high‐performance luminous perovskites (or metal halides) by manipulating the exciton–phonon interaction.
