Synthesis and luminescence of Cs2HfCl6 micro- and Cs2HfF6 nanoparticles

Fellener, Madeleine; Lauria, A.

doi:10.1039/d1tc05734k

Cited by 7 publications

(9 citation statements)

References 61 publications

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“…Fellner and Lauria recently observed a broad emission centered at 489 nm from CHF without a prominent peak, which was considered as defect-related luminescence. [35] The broad emissions observed here have different characters, which are similar to the broad emissions from STEs as reported in the CHC host in the literature. [15][16][17][18][19] The STE emission is centered at 452 nm in CHC.…”

Section: Photoluminescencesupporting

confidence: 83%

“…It is shown that CHF is the most stable one based on its lowest enthalpy of formation in this series of compounds, which was supported experimentally by Fellner and Lauria recently that CHF has higher thermal stability than CHC. [ 35 ]…”

Section: Resultsmentioning

confidence: 99%

“…Recently, Fellner and Lauria synthesized CHF nanoparticles and CHC microparticles using organic precursors at 160 and 100 °C, respectively. [ 35 ] They found that CHF is less hygroscopic and more thermally stable than CHC, as CHF retained its crystal structure after calcinating at 240 °C in air, while CHC transformed to a mixture of CHC and CsCl after calcinating at 240 °C. The synthesized CHF with 2.5 mol% of Eu 3+ showed an impurity phase with the double perovskite structure; while in PL, no Eu 3+ emissions were observed in the synthetic sample.…”

Section: Introductionmentioning

confidence: 99%

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Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs₂HfF₆ Doped with Rare Earths for Radiation Detection

Adhikari

Shrivastava

McClain

et al. 2022

Advanced Optical Materials

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Perovskite materials possess diversified structures, with a virtue of customizable chemical compositions to generate versatile chemical, mechanical, and physical properties. Traditional lead halide perovskites with the general formula APbX 3 , where A is an organic (CH 3 NH 3 + , CH(NH 2 ) 2 + ) or inorganic cation (Cs + ), and X is a halide (I − , Br − , or Cl − ), [1] have received much research as solar cells and optical materials. [2][3][4] However, the facts of toxicity and low stability of these materials have urged researchers to quest for other perovskite systems.Cs 2 HfCl 6 (CHC) is a type of Pb-free material with a vacancy-ordered double perovskite structure, with a space group of 3 Fm m (No. 225). [5] Compared with other double perovskites such as Cs 2 AgBiX 6 (X = Cl, Br) without vacancy, [6][7][8] the CHC in a 2:1:6 atomic ratio contains unoccupied B′ sites when expressed as A 2 BB′X 6 , with a low mass density of 3.56 g cm -3 . [9] This type of material with a vacancy-ordered double perovskite structure has received increasingly renewed attention in the past years. [10][11][12][13] Burger et al. have grown CHC single crystals, which were nonhygroscopic but could give high light yield by γ-rays without any intentional doping. [14] The scintillation was centered at 400 nm, with a principal decay time of 4.37 µs. Through first-principles calculations, Kang and Biswas found that although its bandgap is large (6.34 eV), the luminescence is originated from self-trapped excitons (STEs) that are caused by (HfCl 6 ) 2octahedra trapping localized carries. [15] Further, using undoped CHC single crystals, Král et al. identified photoluminescence (PL) emission bands at 380 nm by STEs, and 460 nm by defects. [16] The emissions could be tuned through dopants. [17][18][19] The CHC material has been widely studied as scintillators [14,[20][21][22][23][24][25][26][27] and light-emitting diodes (LEDs) applications. [17] Besides, other halides in this family, Cs 2 HfBr 6 (CHB) [28] and Cs 2 HfI 6 (CHI), [29,30] have also been reported as scintillators.However, the research on Cs 2 HfF 6 (CHF), the first member of the halide Cs 2 HfX 6 family, is much limited compared to other members. Unlike CHC, CHB, and CHI with a double perovskite structure, CHF crystalized as a hexagonal Bravais Compared to halides Cs 2 HfX 6 (X = Cl, Br, I) with a vacancy-ordered cubic double perovskite structure, the halide Cs 2 HfF 6 (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...

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Section: Photoluminescencesupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs₂HfF₆ Doped with Rare Earths for Radiation Detection

Adhikari

Shrivastava

McClain

et al. 2022

Advanced Optical Materials

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“…24 The weak excitation band in the range of 300 nm to 400 nm and the emission band at 570 nm of Cs 2 ZrCl 6 might be originated from sub-band gap defects owing to the Zr 4+ or Cl À vacancies, which are similar to Cs 2 HfX 6 (X = F, Cl) nanocrystals and Cs 2 TiI 6 . 17,25,26 The reasons are as follows: (1) as Zr, Hf and Ti belong to the group IV elements and have similar chemical characteristics, Cs 2 ZrCl 6 may also be a defectintolerant semiconductor, which is similar to Cs 2 TiI 6 and Cs 2 HfX 6 (X = F, Cl). Therefore, the defect level produced by the Zr 4+ and Cl À vacancies might occur deep in the band gap and localize potential mobile charge carriers.…”

Section: Optical Propertiesmentioning

confidence: 99%

“…30,31 Additionally, according to the Kubelka-Munk function and the Tauc relationship, the direct optical band gap of Cs 2 ZrCl 6 was calculated to be 2.78 eV; (3) as reported in Cs 2 HfF 6 nanopowders, doping Eu 3+ or Mn 2+ did not produce the characteristic emission of doped ions, but increased the emission intensity of defects in Cs 2 HfF 6 , which is due to an increase in defects thanks to the difference in charge between Hf 4+ and Eu 3+ / Mn 2+ . 26 Hence, we synthesized a series of Cs 2 ZrCl 6 :M (M = Ho 3+ , Tm 3+ , Dy 3+ , Er 3+ , Mn 2+ ) to further confirm the existence of defects and the influence of different ions on defects. As shown in Fig.…”

Section: Optical Propertiesmentioning

confidence: 99%

Energy transfer from self-trapped excitons to rare earth ions in Cs₂ZrCl₆perovskite variants

et al. 2023

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Light Emission from Low‐Dimensional Pb‐Free Perovskite‐Related Metal Halide Nanocrystals

Ray

Trizio

Zito

et al. 2022

Advanced Optical Materials

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Hence, low-D compounds (Figure 1) that we will examine here are composed of metal halide polyhedra connected along a plane (2D), a line (1D), or that are even isolated from each other (0D). The reduced connectivity (with respect to 3D systems) leads to the confinement of the excitonic wavefunction, thus to high excitonic binding energies. [1,2] In this review article, we turn our attention to a specific set of low-D materials, i.e., those that are synthesized in the form of colloidal nanocrystals (NCs). For this reason, we are not considering low-D materials in which the inorganic units (layers, chains, or individual polyhedra) are separated from each other by large organic cation spacers (such as butylammonium, phenethylammonium, etc.), as all those compounds tend to crystallize in micron-size crystals, at least along one dimension. Instead, our focus will be mainly on low-D materials containing small monovalent cations (Cs + , Rb + , methylammonium, formamidinium), for which the growth in the form of colloidal NCs is now well established.Additionally, we will not cover low-D metal halides based on Pb, as they have been amply discussed in other review and perspective articles and we will focus instead on the many structures and compositions comprising alternative, less toxic metals. To set the ground for the discussion, we will start by providing a general description of the concepts related to lightIn recent years remarkable progress has been made on developing lowdimensional perovskite-related materials. In particular, with the aim of going toward compounds with low toxicity, various low-dimensional metal halide nanocrystals have been synthesized and investigated. These nanocrystalline compounds crystallize in a plethora of structures and dimensionalities, in many cases with exciting optical properties. Thanks to their photoluminescence emission, which is typically broad and largely Stokes-shifted, such nanocrystals can find applications in indoor lighting, scintillators and luminescent solar concentrators. In this review, recent developments leading to the improvement/management of light emission from such low-dimensional metal halide nanocrystals are highlighted and the possible origin of their light emission is discussed. Furthermore, parallels with their bulk counterparts are drawn and an outlook on what is still worth exploring/studying in this field of research is provided.

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Synthesis and luminescence of Cs₂HfCl₆ micro- and Cs₂HfF₆ nanoparticles

Abstract: Hafnium-based halide crystals are attractive wide-bandgap phosphor materials for scintillation applications due to their high density, low hygroscopicity and bright radioluminescence. Here, we describe synthetic approaches towards the formation of...

Cited by 7 publications

References 61 publications

Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs₂HfF₆ Doped with Rare Earths for Radiation Detection

Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs₂HfF₆ Doped with Rare Earths for Radiation Detection

Energy transfer from self-trapped excitons to rare earth ions in Cs₂ZrCl₆perovskite variants

Light Emission from Low‐Dimensional Pb‐Free Perovskite‐Related Metal Halide Nanocrystals

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Synthesis and luminescence of Cs2HfCl6 micro- and Cs2HfF6 nanoparticles

Abstract: Hafnium-based halide crystals are attractive wide-bandgap phosphor materials for scintillation applications due to their high density, low hygroscopicity and bright radioluminescence. Here, we describe synthetic approaches towards the formation of...

Cited by 7 publications

References 61 publications

Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs2HfF6 Doped with Rare Earths for Radiation Detection

Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs2HfF6 Doped with Rare Earths for Radiation Detection

Energy transfer from self-trapped excitons to rare earth ions in Cs2ZrCl6perovskite variants

Light Emission from Low‐Dimensional Pb‐Free Perovskite‐Related Metal Halide Nanocrystals

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Synthesis and luminescence of Cs₂HfCl₆ micro- and Cs₂HfF₆ nanoparticles

Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs₂HfF₆ Doped with Rare Earths for Radiation Detection

Luminescence from Self‐Trapped Excitons and Energy Transfers in Vacancy‐Ordered Hexagonal Halide Perovskite Cs₂HfF₆ Doped with Rare Earths for Radiation Detection

Energy transfer from self-trapped excitons to rare earth ions in Cs₂ZrCl₆perovskite variants