skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs 2 HfF 6 Doped with Rare Earths for Radiation Detection
Title: Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs 2 HfF 6 Doped with Rare Earths for Radiation Detection
Abstract Compared to halides Cs2HfX6(X = Cl, Br, I) with a vacancy‐ordered cubic double perovskite structure, the halide Cs2HfF6(CHF), with a hexagonal Bravais lattice, possesses a higher mass density and chemical stability for radiation detection. Luminescence properties and energy transfer mechanisms of rare‐earths‐doped CHF materials are studied here. The structure of CHF is identified as a new type of vacancy‐ordered hexagonal perovskite, with the same type of building blocks of the double perovskite but stacked with single layers. Density‐functional theory calculations reveal a large bandgap of CHF. A broad emission is observed from the pristine CHF host, which is suggested to be associated with self‐trapped excitons (STEs). A series of rare‐earths‐doped materials are designed utilizing the STE emissions, and efficient energy transfers from STEs and Tb3+to Eu3+are achieved for tunable emissions. The codoped material shows stable emission under X‐ray irradiation, with 10.2% reduction from its initial emission intensity, associated with possible structural evolution by radiation‐induced deformation of the soft host. The radiation responses of singly and codoped materials are evaluated, and the codoped material is found to be more sensitive to the radiation energy than the singly doped or pristine CHF for radiation detection.  more » « less
Award ID(s):
1900837 1626376
PAR ID:
10373209
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Advanced Optical Materials
Volume:
10
Issue:
19
ISSN:
2195-1071
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Journal of Materials Chemistry C)
    null (Ed.)
    Development of new host materials containing heavy elements for radiation detection is highly desirable. In this work, dibarium octafluorohafnate, Ba 2 HfF 8 , doped with rare-earth ions, was synthesized as cube-shaped nanocrystals via a facile hydrothermal method. The host lattice contains two Ba 2+ crystallographic sites, and dopants on these sites exhibit site-dependent photoluminescence (PL), cathodoluminescence (CL) and X-ray excited radioluminescence (RL) characteristics. Single doping contents were optimized as 25 mol% Tb 3+ and 5 mol% Eu 3+ . In Ba 2 HfF 8 :Tb 3+ –Eu 3+ codoped nanocrystals, preferrable occupation of Eu 3+ and Tb 3+ at two different Ba 2+ sites in the host lattice was observed. The nanocubes exhibited enhanced emissions over micron sized particles. In PL, the presence of Tb 3+ ions significantly enhanced the emission intensity of Eu 3+ ions due to energy transfer from the Tb 3+ to Eu 3+ ions, while under high-energy irradiation in CL or RL, Tb 3+ emission was intensified. X-ray induced RL with afterglow in seconds was observed. It was found that the codoped sample showed higher sensitivity than the singly doped sample, indicating that codoping is an effective strategy to develop a scintillator with this host structure for high-energy radiation detection. 
    more » « less
  2. ; ; ; ; ; ; ; (, Journal of Materials Chemistry C)
    Mn2+/Cr3+codoped Cs2AgInCl6double perovskite were synthesizedviaa facile hydrothermal method, which exhibits two photoluminescence bands with a wide emission switch ranging from orange to NIR and the photoluminescence quantum yield of 49.3%. 
    more » « less
  3. ; ; ; ; ; ; (, Advanced Optical Materials)
    Abstract Lead halide perovskites have recently attracted intensive attention as competitive alternative candidates of legacy compound materials CdTe, CdZnTe, and TlBr for high sensitivity energy‐resolving gamma‐ray detection at room temperature. However, the use of lead in these lead halide perovskites, which is necessary for increasing the stopping power of gamma radiation, poses a serious environmental concern due to the high toxicity of lead. In this regard, environmental‐friendly perovskite‐based gamma‐ray detector materials with key energy‐resolving capabilities are highly desired. Here, the gamma energy‐resolving performance of a new class of all‐inorganic and lead‐free Cs2AgBiBr6double perovskite single crystals (SCs) is reported. Two types of Cs2AgBiBr6SCs, prepared by Bi‐normal and Bi‐poor precursor solutions, respectively, have been grown. Their mobilities and response to gamma radiation are presented. Density of trap states in Bi‐poor Cs2AgBiBr6SCs (2.65 × 109 cm−3) is one order of magnitude lower than that in Bi‐normal Cs2AgBiBr6SCs (3.85 × 1010 cm−3). Using laser‐induced photocurrent measurements, the obtained mobility–lifetime (μ–τ) product in Bi‐poor Cs2AgBiBr6SCs is 1.47 × 10−3 cm2 V−1, indicating their great potentials for gamma‐ray detection. Further, the fabricated detector based on Bi‐poor Cs2AgBiBr6SC shows response to 59.5 keV gamma‐ray with an energy resolution of 13.91%. 
    more » « less
  4. ; ; ; ; ; (, Journal of Materials Chemistry C)
    null (Ed.)
    In this paper, the photoluminescent properties of a lead-free double perovskite Cs 2 NaInCl 6 doped with Sb 3+ are explored. The host crystal structure is a cubic double perovskite with Fm 3̄ m symmetry, a = 10.53344(4) Å, and rock salt ordering of Na + and In 3+ . It is a wide bandgap compound ( E g ≈ 5.1 eV), and substitution with Sb 3+ leads to strong absorption in the UV due to localized 5s 2 → 5s 1 5p 1 transitions on Sb 3+ centers. Radiative relaxation back to the 5s 2 ground state, via a 3 P 1 → 1 S 0 transition, leads to intense blue luminescence, centered at 445 nm, with a photoluminescent quantum yield of 79%. The Stokes shift of 0.94 eV is roughly 33% smaller than it is in the related vacancy ordered double perovskite Cs 2 SnCl 6 . The reduction in Stokes shift is likely due to a change in coordination number of Sb 3+ from 6-coordinate in Cs 2 NaInCl 6 to 5-coordinate in Cs 2 SnCl 6 . In addition to the high quantum yield, Cs 2 NaInCl 6 :Sb 3+ exhibits excellent air/moisture stability and can be prepared from solution; these characteristics make it a promising blue phosphor for applications involving near-UV excitation. 
    more » « less
  5. ; ; ; ; ; ; ; ; (, Advanced Functional Materials)
    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
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email