skip to main content

Title: Rb 2 CuX 3 (X = Cl, Br): 1D All‐Inorganic Copper Halides with Ultrabright Blue Emission and Up‐Conversion Photoluminescence

All‐inorganic metal halides such as Cs4PbX6and CsPbX3(X = Cl, Br, and I) are attracting global attention owing to their promise in optoelectronic applications. However, the presence of the toxic heavy metal lead (Pb) in these materials is a major concern. Here, a family of nontoxic high‐efficiency blue‐emitting all‐inorganic halides Rb2CuX3(X = Br and Cl) is reported; the compounds exhibit 1D crystal structures featuring anionic2−ribbons separated by Rb+cations. The measured record high photoluminescence quantum yield values range from 64% to 100% for Rb2CuBr3and Rb2CuCl3, respectively. Furthermore, the measured emission linewidths are quite narrow with full width at half maximum values of 54 and 52 nm for Rb2CuBr3and Rb2CuCl3, respectively. Single crystals of Rb2CuCl3demonstrate an anti‐Stokes photoluminescence signal, shown for the first time for Pb‐free metal halides. The discovery of highly efficient narrow blue emitters based on a nontoxic and inexpensive metal copper paves a way for the consideration of low‐cost and environmentally friendly copper halides for practical applications.

more » « less
Award ID(s):
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Optical Materials
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Copper(I) halides are emerging as attractive alternatives to lead halide perovskites for optical and electronic applications. However, blue‐emitting all‐inorganic copper(I) halides suffer from poor stability and lack of tunability of their photoluminescence (PL) properties. Here, the preparation of silver(I) halides A2AgX3(A = Rb, Cs; X = Cl, Br, I) through solid‐state synthesis is reported. In contrast to the Cu(I) analogs, A2AgX3are broad‐band emitters sensitive to A and X site substitutions. First‐principle calculations show that defect‐bound excitons are responsible for the observed main PL peaks in Rb2AgX3and that self‐trapped excitons (STEs) contribute to a minor PL peak in Rb2AgBr3. This is in sharp contrast to Rb2CuX3, in which the PL is dominated by the emission by STEs. Moreover, the replacement of Cu(I) with Ag(I) in A2AgX3significantly improves photostability and stability in the air under ambient conditions, which enables their consideration for practical applications. Thus, luminescent inks based on A2AgX3are prepared and successfully used in anti‐counterfeiting applications. The excellent light emission properties, significantly improved stability, simple preparation method, and tunable light emission properties demonstrated by A2AgX3suggest that silver(I) halides may be attractive alternatives to toxic lead halide perovskites and unstable copper(I) halides for optical applications.

    more » « less
  2. Abstract

    All‐inorganic lead halide perovskite nanocrystals (NCs) have great optoelectronic properties with promising applications in light‐emitting diodes (LEDs), lasers, photodetectors, solar cells, and photocatalysis. However, the intrinsic toxicity of Pb and instability of the NCs impede their broad applications. Shell‐coating is an effective method for enhanced environmental stability while reducing toxicity by choosing non‐toxic shell materials such as metal oxides, polymers, silica, etc. However, multiple perovskite NCs can be encapsulated within the shell material and a uniform epitaxial‐type shell growth of well‐isolated NCs is still challenging. In this work, lead‐free vacancy‐ordered double perovskite Cs2SnX6(X = Cl, Br, and I) shells are epitaxially grown on the surface of CsPbX3NCs by a hot‐injection method. The effectiveness of the non‐toxic double perovskite shell protection is demonstrated by the enhanced environmental and phase stability against UV illumination and water. In addition, the photoluminescence quantum yields (PL QYs) increase for the CsPbCl3and CsPbBr3NCs after shelling because of the type I band alignment of the core/shell materials, while enhanced charge transport properties obtained from CsPbI3/Cs2SnI6core/shell NCs are due to the efficient charge separation in the type II core/shell band alignment.

    more » « less
  3. null (Ed.)
    The past decade has witnessed tremendous advances in synthesis of metal halide perovskites and their use for a rich variety of optoelectronics applications. Metal halide perovskite has the general formula ABX 3 , where A is a monovalent cation (which can be either organic ( e.g. , CH 3 NH 3 + (MA), CH(NH 2 ) 2 + (FA)) or inorganic ( e.g. , Cs + )), B is a divalent metal cation (usually Pb 2+ ), and X is a halogen anion (Cl − , Br − , I − ). Particularly, the photoluminescence (PL) properties of metal halide perovskites have garnered much attention due to the recent rapid development of perovskite nanocrystals. The introduction of capping ligands enables the synthesis of colloidal perovskite nanocrystals which offer new insight into dimension-dependent physical properties compared to their bulk counterparts. It is notable that doping and ion substitution represent effective strategies for tailoring the optoelectronic properties ( e.g. , absorption band gap, PL emission, and quantum yield (QY)) and stabilities of perovskite nanocrystals. The doping and ion substitution processes can be performed during or after the synthesis of colloidal nanocrystals by incorporating new A′, B′, or X′ site ions into the A, B, or X sites of ABX 3 perovskites. Interestingly, both isovalent and heterovalent doping and ion substitution can be conducted on colloidal perovskite nanocrystals. In this review, the general background of perovskite nanocrystals synthesis is first introduced. The effects of A-site, B-site, and X-site ionic doping and substitution on the optoelectronic properties and stabilities of colloidal metal halide perovskite nanocrystals are then detailed. Finally, possible applications and future research directions of doped and ion-substituted colloidal perovskite nanocrystals are also discussed. 
    more » « less
  4. Abstract

    The all‐inorganic metal halide perovskite CsPbX3(X = Cl, Br, and I) has received extensive attention in the field of white light‐emitting diodes (WLEDs) due to its high luminous intensity and high color purity. However, the shortcoming of poor stability directly affects the luminous performance of the WLED devices and reduces their luminous efficiency, which has become an urgent problem to be solved. Here, three‐color lead halide perovskite phosphors (blue‐emitting CsPbBr3synthesized at 20 °C (CPB‐20), green‐emitting CsPbBr3‐80 (CPB‐80)/CsPbBr3:SCN(CPB:SCN), and red‐emitting PEA2PbBr4(PPB)/PEA2PbBr4:Mn2+(PPB:Mn2+)) with higher stability and luminous intensity are simultaneously prepared and applied in WLEDs. Density functional theory is used to optimize the structures of CsPbBr3and PEA2PbBr4, and to calculate the work function, optical properties, and charge density difference. Not only the WLED devices with three‐color lead halide perovskite phosphors are constructed, but also WLED devices from warm white to cold white are realized by tuning the ratio of the different emissions, and a superior color quality (color rendering index of 96) and ideal correlated color temperature (CCT of 9376 K) are achieved. This work will set the stage for exploring low‐cost, environmentally friendly, high‐performance WLEDs.

    more » « less
  5. Abstract

    Post‐synthesis anion exchange of all‐inorganic cesium lead halide perovskite nanocrystals (CsPbX3NCs, where X=Cl, Br, and/or I) provides a rapid and simple means of tuning their band gap and photoluminescence emission wavelengths. Here we report color‐shifting of CsPbX3nanocrystals induced by a macromolecular source of halide ions, specifically using polystyrene with ammonium halides as pendent groups. This strategy for introducing new halides to the perovskite nanocrystals gave access to perovskite‐polymer hybrid materials as solutions, thin films, or free‐flowing powders. Spectroscopic measurements of the halide‐exchanged nanocrystal products revealed high photoluminescence quantum yields across the visible spectrum, with exchange kinetics that were tunable based on the solution environment, suggesting an aggregation‐inhibited exchange process that affords access to multi‐colored solutions and films.

    more » « less