Possibility of Luminescent Quantum Yields Greater than Unity

Dexter, D. L.

doi:10.1103/physrev.108.630

Cited by 248 publications

(129 citation statements)

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“…This cooperative sensitisation process was predicted in 1957 by Dexter [10] but it was only recently that a paper has been published in which the occurrence of cooperative sensitisation (or second-order downconversion) was presented [11]. A promising system to study second-order energy-transfer processes is the combination of one Tb 3+ and two Yb 3+ ions: the Tb 3+ 5 D 4 !…”

Section: Cooperative Sensitizationmentioning

confidence: 99%

Photon management with lanthanides

et al. 2006

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Efficient conversion of photons from high energy radiation (e.g. ultraviolet or X-rays) to lower energies (visible) has been optimized by using luminescent materials based on the optical properties of lanthanide ions. Presently, luminescent materials with efficiencies close to the theoretical maximum are applied in e.g. fluorescent tubes, X-ray imaging and color television. Contrary to the mature status of luminescent materials in these fields, areas requiring new luminescent materials are emerging. There is great challenge in research on upand downconversion materials and lanthanide ions are the prime candidates to achieve efficient materials. Here downconversion processes will be discussed for VUV phosphors with Pr 3+ . The efficiency of resonant energy transfer of the 1 S 0 -1 I 6 energy from Pr 3+ to Eu 3+ and Mn 2+ is investigated. The aim is to convert the 405 nm photon of the first step of the well-known cascade emission of Pr 3+ into a more useful visible photon. For co-doping with Eu 3+ it is observed that the Pr 3+ emission is quenched, most probably through a metal-to-metal charge-transfer state. The energy transfer from Pr 3+ to Mn 2+ is found to be inefficient.An alternative for downconversion through resonant energy transfer is the non-resonant process of cooperative sensitization. For the Tb-Yb couple efficient cooperative energy transfer from the 5 D 4 level of Tb 3+ to two Yb 3+ neighbors is observed with a transfer rate of 0.26 ms À1 . This corresponds to an upper limit of 188% for the conversion efficiency of visible (490 nm) photons to infrared ($1000 nm) photons.

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Section: Cooperative Sensitizationmentioning

confidence: 99%

Photon management with lanthanides

et al. 2006

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“…In this process, a high-energy photon is converted into two or more lower-energy photons, with a quantum efficiency of potentially well over 100% 3 . If the downconverted photons are in the visible range, this concept is of interest for color conversion layers in conventional lighting applications 1,2,4-6 .…”

Section: Introductionmentioning

confidence: 99%

Multi-photon quantum cutting in Gd2O2S:Tm3+ to enhance the photo-response of solar cells

Martín-Rodríguez

Zhang

et al. 2015

Light Sci Appl

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Conventional photoluminescence (PL) yields at most one emitted photon for each absorption event. Downconversion (or quantum cutting) materials can yield more than one photon by virtue of energy transfer processes between luminescent centers. In this work, we introduce Gd 2 O 2 S:Tm 31 as a multi-photon quantum cutter. It can convert near-infrared, visible, or ultraviolet photons into two, three, or four infrared photons of ,1800 nm, respectively. The cross-relaxation steps between Tm 31 ions that lead to quantum cutting are identified from (time-resolved) PL as a function of the Tm 31 concentration in the crystal. A model is presented that reproduces the way in which the Tm 31 concentration affects both the relative intensities of the various emission lines and the excited state dynamics and providing insight in the quantum cutting efficiency. Finally, we discuss the potential application of Gd 2 O 2 S:Tm 31 for spectral conversion to improve the efficiency of next-generation photovoltaics. Keywords: downconversion; infrared emission; quantum cutting; solar cells; spectral conversions INTRODUCTION Over the last decade, advanced luminescent materials exhibiting downconversion, also known as quantum cutting or quantum splitting, have been developed 1,2 . In this process, a high-energy photon is converted into two or more lower-energy photons, with a quantum efficiency of potentially well over 100% 3 . If the downconverted photons are in the visible range, this concept is of interest for color conversion layers in conventional lighting applications 1,2,4-6 . New exciting possibilities of downconversion to infrared (IR) photons lie in next-generation photovoltaics, aiming at minimizing the spectral mismatch losses in solar cells [7][8][9][10][11] .Spectral mismatch is the result of the broad width of the spectrum emitted by the sun. Semiconductor absorber materials absorb only photons with an energy hn higher than the band gap E g 7 . To absorb many photons and produce a large electrical current, absorber materials must therefore have a small bandgap. However, because excited charge carriers rapidly thermalize to the edges of a semiconductor's conduction and valence bands, a high voltage output requires an absorber with a large band gap. Hence, materials with low transmission losses (leading to a large current) have high thermalization losses (leading to a low voltage) and vice versa 12,13 . These spectral mismatch losses constitute the major factor defining the relatively low ShockleyQueisser limit 14 , the maximum light-to-electricity conversion efficiency of 33% in a single-junction solar cell, obtained for a band gap of approximately 1.1 eV (1100 nm) 13 .Efficiencies higher than 33% can be reached with multi-junction solar cells, where a stack of multiple absorber materials are each optimized to efficiently convert different parts of the solar spectrum to

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“…В настоящей работе мы продолжили изучение новых возможных механизмов фотонного умножения, исследуя впервые предложенный Декстером процесс сенсибилизационной передачи энергии от одного иона-сенсибилизатора двум люминесцирующим ионам [11]. Неоднократные попытки экспериментального подтверждения механизма Декстера в течение длительного времени оставались безуспешными (см., например, [6]), и лишь в 2001 г. в легированных ионами Yb 3+ сложных матрицах были найдены его экспериментальные подтверждения [12].…”

Section: аннотацияunclassified

Low-temperature investigation of electronic excitations in wide-gap materials doped with RE3+ or Cr3+ ions

Lushchik

Kudryavtseva

et al. 2011

Opt. Spectrosc.

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Possibility of Luminescent Quantum Yields Greater than Unity

Cited by 248 publications

References 2 publications

Photon management with lanthanides

Photon management with lanthanides

Multi-photon quantum cutting in Gd2O2S:Tm3+ to enhance the photo-response of solar cells

Low-temperature investigation of electronic excitations in wide-gap materials doped with RE3+ or Cr3+ ions

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