First-principles study of luminescence in Ce-doped inorganic scintillators

Canning, Andrew; Chaudhry, A.; Boutchko, Rostyslav; Grønbech‐Jensen, Niels

doi:10.1103/physrevb.83.125115

Cited by 138 publications

(148 citation statements)

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“…[19][20][21] The plane wave energy cutoff was set to 230 eV and Gaussian smearing with a width of 0.1 eV was used to determine occupation numbers.…”

Section: Methodology a General Computational Parametersmentioning

confidence: 99%

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First-principles study of codoping in lanthanum bromide

et al. 2015

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Co-doping of Ce-doped LaBr3 with Ba, Ca, or Sr improves the energy resolution that can be achieved by radiation detectors based on these materials. Here, we present a mechanism that rationalizes of this enhancement that on the basis of first principles electronic structure calculations and point defect thermodynamics. It is shown that incorporation of Sr creates neutral VBr − SrLa complexes that can temporarily trap electrons. As a result, Auger quenching of free carriers is reduced, allowing for a more linear, albeit slower, scintillation light yield response. Experimental Stokes shifts can be related to different CeLa − SrLa − VBr triple complex configurations. Co-doping with other alkaline as well as alkaline earth metals is considered as well. Alkaline elements are found to have extremely small solubilities on the order of 0.1 ppm and below at 1000 K. Among the alkaline earth metals the lighter dopant atoms prefer interstitial-like positions and create strong scattering centers, which has a detrimental impact on carrier mobilities. Only the heavier alkaline earth elements (Ca, Sr, Ba) combine matching ionic radii with sufficiently high solubilities. This provides a rationale for the experimental finding that improved scintillator performance is exclusively achieved using Sr, Ca, or Ba. The present mechanism demonstrates that co-doping of wide gap materials can provide an efficient means for managing charge carrier populations under out-of-equilibrium conditions. In the present case dopants are introduced that manipulate not only the concentrations but the electronic properties of intrinsic defects without introducing additional gap levels. This leads to the availability of shallow electron traps that can temporarily localize charge carriers, effectively deactivating carrier-carrier recombination channels. The principles of this mechanism are therefore not specific to the material considered here but can be adapted for controlling charge carrier populations and recombination in other wide gap materials.

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“…[19][20][21] The plane wave energy cutoff was set to 230 eV and Gaussian smearing with a width of 0.1 eV was used to determine occupation numbers.…”

Section: Methodology a General Computational Parametersmentioning

confidence: 99%

“…Excited Ce-4f 0 states were obtained in a similar approach as used by Canning and co-workers.. 20,23 First, a subspace of Ce-4f states is identified by selecting states whose projection onto spherical harmonics with l = 3 exceeds a suitably chosen threshold. This is made possible by the localized nature of the rare-earth 4f states.…”

Section: B Excited Statesmentioning

confidence: 99%

First-principles study of codoping in lanthanum bromide

et al. 2015

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“…[9] Recently, Canning and co-authors used CDFT to identify several promising hosts for efficient scintillators, but they did not study the emission and Stokes shifts. [10] In the present work, we assess the generality and accuracy of the proposed theoretical method, and compare it with Dorenbos' semi-empirical model. To do so, firstly we study from first principles the absorption, emission and Stokes shift of a set of thirteen representative Ce 3+ -doped materials that include oxides, nitrides and halides, and that span a large range of transition energies, from 2 to 5 eV.…”

mentioning

confidence: 99%

Assessment of First‐Principles and Semiempirical Methodologies for Absorption and Emission Energies of Ce³⁺‐Doped Luminescent Materials

Jia

Poncé

Miglio

et al. 2017

Advanced Optical Materials

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Abstract:In search of a reliable methodology for the prediction of light absorption and emission of Ce 3+ -doped luminescent materials, thirteen representative materials are studied with first-principles and semi-empirical approaches. In the first-principles approach, that combines constrained density-functional theory and ∆SCF, the atomic positions are obtained for both ground and excited states of the Ce 3+ ion. The structural information is fed into Dorenbos' semi-empirical model. Absorption and emission energies are calculated with both methods and compared with experiment. The first-principles approach matches experiment within 0.3 eV, with two exceptions at 0.5 eV. In contrast, the semi-empirical approach does not perform as well (usually more than 0.5 eV error). The general applicability of the present first-principles scheme, with an encouraging predictive power, opens a novel avenue for crystal site engineering and high-throughput search for new phosphors and scintillators. 2The 4f→5d transition of Ce 3+ ion has been widely used in the design of efficient luminescent systems such as white LED phosphors, scintillators and laser materials due to its spin-allowed character and its tunability as a function of the host material. [1-6] Until now, most of the efforts to find new hosts relied on trial and error. An accurate and efficient methodology to design new materials would be a remarkable achievement. With this idea in mind, a semi-empirical model has been proposed by Dorenbos, to describe Ce 3+ luminescence in inorganic compounds. [7] This semi-empirical model provides correct general trend for absorption.Unfortunately, it suffers from several drawbacks. First, its quantitative predictions rely on some fitting parameters, which have been determined only for oxide, nitride and fluoride materials at present.[6] Second, the semi-empirical model fails to predict the emission energy and Stokes shift. This limitation is due to missing experimental relaxed structure configurations in the excited state. These two shortcomings result in limited accuracy and scope of the semi-empirical approach.In a recent paper, we have explored a first-principles alternative to overcome the drawbacks of Dorenbos' semi-empirical model. [8] The successful quantitative description of the neutral excitation, emission energy and Stokes shift in two Ce 3+ -doped lanthanum silicate nitrides has been realized. Our approach is based on constrained density functional theory (CDFT) and the ∆SCF methods, following the early work by Marsman. [9] Recently, Canning and co-authors used CDFT to identify several promising hosts for efficient scintillators, but they did not study the emission and Stokes shifts. [10] In the present work, we assess the generality and accuracy of the proposed theoretical method, and compare it with Dorenbos' semi-empirical model. To do so, firstly we study from first principles the absorption, emission and Stokes shift of a set of thirteen representative Ce 3+ -doped materials that include oxides, nitrides and halid...

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“…11,12 In spite of all the efforts, [13][14][15][16][17] some aspects of the conversion mechanism are still unclear. For example, energy resolution of inorganic scintillators is still much larger than the fundamental limit dictated by photon statistics.…”

Section: Introductionmentioning

confidence: 99%

Energy resolution and related charge carrier mobility in LaBr3:Ce scintillators

Khodyuk

Quarati

Alekhin

et al. 2013

Journal of Applied Physics

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The scintillation response of LaBr 3 :Ce scintillation crystals was studied as function of temperature and Ce concentration with synchrotron X-rays between 9 keV and 100 keV. The results were analyzed using the theory of carrier transport in wide band gap semiconductors to gain new insights into charge carrier generation, diffusion, and capture mechanisms. Their influence on the efficiency of energy transfer and conversion from X-ray or c-ray photon to optical photons and therefore on the energy resolution of lanthanum halide scintillators was studied. From this, we will propose that scattering of carriers by both the lattice phonons and by ionized impurities are key processes determining the temperature dependence of carrier mobility and ultimately the scintillation efficiency and energy resolution. When assuming about 100 ppm ionized impurity concentration in 0.2% Ce 3þ doped LaBr 3, mobilities are such that we can reproduce the observed temperature dependence of the energy resolution, and in particular, the minimum in resolution near room temperature is reproduced. V C 2013 AIP Publishing LLC. [http://dx

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First-principles study of luminescence in Ce-doped inorganic scintillators

Cited by 138 publications

References 80 publications

First-principles study of codoping in lanthanum bromide

First-principles study of codoping in lanthanum bromide

Assessment of First‐Principles and Semiempirical Methodologies for Absorption and Emission Energies of Ce³⁺‐Doped Luminescent Materials

Energy resolution and related charge carrier mobility in LaBr3:Ce scintillators

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First-principles study of luminescence in Ce-doped inorganic scintillators

Cited by 138 publications

References 80 publications

First-principles study of codoping in lanthanum bromide

First-principles study of codoping in lanthanum bromide

Assessment of First‐Principles and Semiempirical Methodologies for Absorption and Emission Energies of Ce3+‐Doped Luminescent Materials

Energy resolution and related charge carrier mobility in LaBr3:Ce scintillators

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Assessment of First‐Principles and Semiempirical Methodologies for Absorption and Emission Energies of Ce³⁺‐Doped Luminescent Materials