Quantum Cutting Research Articles

Downconversion from visible to near infrared through multi-wavelength excitation in Er3+/Yb3+ co-doped NaYF4 nanocrystals

Homogeneous NaYF4:Yb3+/Er3+ nanoparticles (NPs) with average diameters of ∼10 nm and ∼200 nm and various doping concentrations (Yb3+:0%−20%, Er3+:2%) were prepared by the thermal decomposition of trifluoroacetate precursors. The visible and infrared (IR) emission spectra range of 500–2200 nm and luminescent dynamics were studied through the pumping of multi-wavelengths, 443 nm, 488 nm, and 520 nm. Strong and sufficient IR emissions were observed, including the transitions of 4I11/2−4I15/2 at ∼980 nm, 2H11/2−4I11/2 at ∼1112 nm, 4S3/2−4I11/2 at ∼1217 nm, 4I13/2−4I15/2 at ∼1540 nm, 4I9/2−4I13/2 at ∼1680 nm, and 4F9/2−,4I11/2 at ∼1955 nm. It is the first observation of 2H11/2−4I11/2 and 4F9/2−4I11/2 emissions to our knowledge. Through the IR emissions, several novel channels of quantum cutting (QC) were evidenced, including: (1) 2H11/2−4I11/2 and 4I11/2−4I15/2, (2) 4S3/2−4I11/2 and 4I11/2−4I15/2, (3) 4F9/2−4I11/2 and 4I11/2−4I15/2, and (4) 4I9/2−4I13/2 and 4I13/2−4I15/2. For the IR QC emissions, the overall efficiencies in the 200−nm NaYF4:Yb3+, Er3+ were estimated to be as high as 186−193%. Through the measurements of luminescent dynamics of Er3+ on different levels, the spontaneous rates and energy transfer (ET) rates from Er3+ to Yb3+ were determined, which showed that ET from Er3+ to Yb3+ mainly happened on 2H11/2,4S3/2, and 4I13/2 levels. The present results indicate that the visible-to-IR QC for Er3+ has potential use to improve the efficiency of some IR solar cells, such as germanium-based ones.

Increased downconversion efficiency and improved near infrared emission by different charge compensations in CaMoO 4:Yb 3+ powders

All of the samples were synthesized by sol-gel methods. Two approaches to charge compensation, (i) 2Ca 2+→Yb 3++M +, where M + is an alkali ion like Li +, Na + and K +, and (ii) indirect charge compensation: 3Ca 2+→2Yb 3++vacancy, were studied in detail. It was found that charge compensation would be very beneficial for the growth of the grains, especially in Li + ions added samples. All the grains were homogeneously spherical with less boundaries; in addition, a great variety of the absorption ability in different charge compensation samples were observed: in comparison with the phosphors without charge compensation, indirectly charge compensated and Li + ions added phosphors showed much stronger absorption strength in the ultraviolet (UV) region whereas that of Na + and K + ions added samples was much weaker; moreover, measurements of the emission intensities showed that: in comparison with the phosphors without charge compensation, the visible emission intensity from MoO 4 2− decreased a lot in indirectly charge compensated and Li + ions added phosphors, whereas there was a remarkable increase of the near infrared (NIR) emission intensity from Yb 3+ ions in the two types of samples under 266 nm excitation, implying more efficient energy transfer (ET) from MoO 4 2− to Yb 3+ ions; at last, measurements and analysis of the decay curves of the visible 495 nm emission were carried out, and it was found that the energy transfer from MoO 4 2− to Yb 3+ ions were more efficient in the two above types of phosphors. The theoretical quantum cutting (QC) efficiency was also improved greatly. Overall, the addition of Li + ions would be very beneficial for the morphology of the powders in addition to the growth of the grains. It was advantageous to increase the downconversion (DC) quantum efficiency; however, indirect charge compensation would enhance the NIR emission intensity to the most for its strongest absorption ability in the UV region.

Near-infrared quantum cutting in Ce3+, Er3+, and Yb3+ doped yttrium silicate powders prepared by combustion synthesis

Yttrium silicate (YS) powders doped with Ce3+, Er3+, and Yb3+ were prepared by combustion synthesis. The material was investigated for use as energy downconverters to reduce thermalization losses in crystalline Si solar cells. The powders were excited by UV light (355 nm), and near-infrared emission around 1 μm was observed corresponding to a quantum cutting (QC) effect. The QC process occurs via cooperative energy transfer from Ce3+ (sensitizer) to Yb3+ (activator) in Ce3+:Yb3+ co-doped YS powders. QC was also observed in Er3+:Yb3+ co-doped YS powder via sequential energy transfer. The idea of synergy by use of Ce3+:Er3+:Yb3+ triply doped system to enhance the QC efficiency was investigated. We observed that the QC performance of Ce3+:Er3+:Yb3+ triply doped YS powder is not superior to that of Ce3+:Yb3+ co-doped YS powder due to near-infrared luminescence quenching induced by energy back-transfer from Yb3+ to Er3+.

Near-Infrared Quantum Cutting Nanophosphors for Solar Cells

An efficient near-infrared (NIR) quantum cutting (QC) nanophospors with Ce3+, Yb3+ codoped in CaF2 had been synthesized by hydrothermal method and characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscopy, photoluminescence spectra and decay dynamics. The nanoparticles were uniform and monodisperse. Under the excitation of 5d level of Ce3+, an intense NIR emission at 900-1050nm was observed which match to the energy of Si band gap of Si - based solar cells. In the Ce3+, Yb3+ codoped CaF2, the lifetime of Ce3+ decreases Superscript textand the quantum efficiency (QE) increases with increasing Yb3+ concentration.

Efficient near-infrared quantum cutting by Ce 3+-Yb 3+ couple in GdBO 3 phosphors

Ce 3+ and Yb 3+ co-activated GdBO 3 phosphors were prepared by a conventional solid-state reaction method. X-ray powder diffraction, photoluminescent spectra and decay curves were used to characterize their structural and luminescent properties. An efficient near-infrared (NIR) quantum cutting (QC) from the phosphors was observed, which involved the emission of two low-energy NIR photons (around 971 nm) from an absorbed ultra-violet (UV) photon at 358 nm via a cooperative energy transfer (CET) from Ce 3+ to Yb 3+ ions. The theoretical quantum efficiency was calculated and the maximum efficiency approached up to 164% before reaching the critical concentration quenching threshold. Our results demonstrated that these phosphors might find potential application in improving the efficiency of silicon based solar cells.

Efficient first-order resonant near-infrared quantum cutting in β-NaYF 4:Ho 3+,Yb 3+

We demonstrated an efficient two-photon near-infrared (NIR) quantum cutting (QC) in Ho 3+–Yb 3+ co-doped hexagonal β-NaYF 4, which could efficiently convert an incident high-energy photon in the wavelength region of 300–550 nm into two NIR photons. Underlying mechanism for the two-photon NIR-QC process is analyzed in terms of static and dynamic photoemission and monitored excitation spectra. It is found that NIR-QC can occur through two possible energy transfer (ET) approaches: (i) the excited Ho 3+: 5F 3 state may simultaneously excite two Yb 3+ neighbors via a cooperative ET process, and (ii) the NIR-QC can be feasibly induced by a first Ho 3+( 5S 2, 5F 4) + Yb 3+( 2F 7/2) → Ho 3+( 5I 6) + Yb 3+( 2F 5/2) resonant ET process and a sequential 5I 6 → 5I 8 transition of Ho 3+. This novel NaYF 4:Ho 3+,Yb 3+ NIR-QC phosphor, may explore a new approach to maximize the performance of solar cells.

ChemInform Abstract: Recent Progress in Quantum Cutting Phosphors

AbstractReview: 386 refs.

Bright green-emitting, energy transfer and quantum cutting of Ba_3Ln(PO_4)_3: Tb^3+ (Ln = La, Gd) under VUV-UV excitation

Tb3+ doped Ba3Gd(PO4)3 and Ba3La(PO4)3 phosphors were synthesized using the traditional high temperature solid state reaction method. The excitation, emission, and decay spectra were measured at room temperature. Efficient energy transfer (ET) from Gd3+ to Tb3+ exists in Tb3+ doped Ba3Gd(PO4)3, and the ET efficiency increases with the increase of Tb3+ concentration. The visible quantum cutting (QC) via cross relaxation was observed upon exciting low-spin (7D(J)) 5d levels of Tb3+ ions. Ba3Tb(PO4)3 sample shows relatively strong emission intensity in comparison with Zn2SiO4: Mn2+ (ZSM) upon 172 nm excitation, and with a decay time τ(1/10) about 6.4 ms under 351 nm excitation, indicating the potential application of this phosphor for plasma display panels (PDPs) and Hg-free lamps.

High efficient near-infrared quantum cutting in Ce 3+,Yb 3+ co-doped LuBO 3 phosphors

High efficient near-infrared (NIR) quantum cutting (QC) LuBO 3:Ce 3+,Yb 3+ phosphors had been synthesized by hydrothermal method with further heat treatment. Due to the cooperative energy transfer (CET) from one Ce 3+ to two Yb 3+ ions, an intense NIR emission around 971 nm of Yb 3+: 2F 5/2 → 2F 7/2 transition was obtained under 369 nm excitation. Yb 3+ concentration dependent quantum efficiency has been calculated and the maximum efficiency approaches up to 181% before reaching the critical concentration quenching threshold. Because the 971 nm emission of Yb 3+ is matched with the band gap of crystalline Si, the phosphors may be applied potentially in silicon-based solar cells.

Near-infrared emission from Eu–Yb doped silicate glasses subjected to thermal reduction

Quantum cutting (QC) is a promising approach for enhancing the energy conversion efficiency of solar cells since it allows for conversion of one ultraviolet photon from the sun into two near-infrared photons with energy comparable to the band gap of silicon solar cells. We find that QC can occur by cooperative energy transfer from Eu2+ to Yb3+ in soda-lime-silicate glasses subjected to thermal reduction around the glass transition temperature. Besides the QC effect, the thermal reduction results in improvement of surface performances, e.g., hardness. This synergy effect potentially makes the thermally reduced glass an ideal solar cell substrate material.

The Quantum Cutting of Tb3+ in Ca6Ln2Na2(PO4)6F2 (Ln = Gd, La) under VUV−UV Excitation: with and without Gd3+

The VUV-vis spectroscopic properties of Tb(3+) activated fluoro-apatite phosphors Ca(6)Ln(2-x)Tb(x)Na(2)(PO(4))(6)F(2) (Ln = Gd, La) were studied. The results show that phosphors Ca(6)Gd(2-x)Tb(x)Na(2)(PO(4))(6)F(2) with Gd(3+) ions as sensitizers have intense absorption in the VUV range. The emission color of both phosphors can be tuned from blue to green by changing the doping concentration of Tb(3+) under 172 nm excitation. The visible quantum cutting (QC) via cross relaxation between Tb(3+) ions was observed in cases with and without Gd(3+). Though QC can be realized in phosphors Ca(6)La(2-x)Tb(x)Na(2)(PO(4))(6)F(2), we found that Gd(3+)-containg phosphors have a higher QC efficiency, confirming that the Gd(3+) ion indeed plays an important role during the quantum cutting process. In addition, the energy transfer process from Gd(3+) to Tb(3+) as well as (5)D(3)-(5)D(4) cross relaxation was investigated and discussed in terms of luminescence spectra and decay curves.

Near infrared downconversion in Pr 3+–Yb 3+ codoped oxyfluoride glass ceramics

The loss mechanism in the Pr 3+–Yb 3+ codoped glass that showed quantum cutting (QC) phenomenon was investigated and we found that the multi-phonon relaxation from Pr 3+: 1G 4 is the major loss to the quantum cutting process. To reduce the loss, Pr 3+–Yb 3+ codoped glass ceramics containing SrF 2 crystals were prepared and quantum yields (QY) of Yb 3+ emission by 440 nm excitation were measured. Only glass ceramics with the highest Yb concentration ( x = 2.9) showed higher QY than that of the as-made glass. It is considered that in low Yb concentration Pr 3+ and Yb 3+ ions were divided into different matrix possibly because of different ionic radius between Pr 3+ and Yb 3+ ions.

Broad-Band Excited Quantum Cutting in Eu2 + – Yb3 + Co-doped Aluminosilicate Glasses

We report the possibility of broad-band spectral modification based on quantum cutting (QC), which converts one UV or visible photon into two near-IR photons in ion co-doped aluminosilicate glasses. Metal Al powder is added to the host glass composition to reduce to during melting in air. The existence of europium in the divalent state has been confirmed by absorption spectroscopy. Excitation and emission spectra as well as fluorescence decay measurements have been carried out to examine the occurrence of cooperative energy transfer from to ions. The QC process in this glass system enables the silicon-based solar cells to more efficiently utilize the solar energy in the broad wavelength region from 250 to 500 nm, where the silicon-based solar cells show a weak response.

Near-infrared quantum cutting via cooperative energy transfer in Gd2O3:Bi3+,Yb3+ phosphors

An efficient near-infrared (NIR) quantum-cutting (QC) by converting broadband ultraviolet (UV) into NIR via cooperative down-conversion (CD) has been demonstrated in Gd2O3:Bi3+,Yb3+ phosphors. Upon excitation of UV photon varying from 320–390 nm, NIR emissions has been obtained from transitions of the transition-metal Bi3+:P31 level to the rare-earths Yb3+:F25/2 level. The authors have analyzed the measured luminescence spectra and decay lifetimes and proposed a mechanism to rationalize the CD effect. Application of the broadband NIR-QC phosphors might greatly enhance response of silicon-based solar cells by means of down-conversion of UV part of the solar spectrum to NIR photons with a twofold increase in the photon number.

Near-infrared quantum cutting in Ce 3+, Yb 3+ co-doped YBO 3 phosphors by cooperative energy transfer

An efficient near-infrared (NIR) quantum cutting (QC) in Ce 3+, Yb 3+ co-doped YBO 3 phosphors has been demonstrated, which involves the emission of two low-energy NIR photons (around 973 nm) from an absorbed ultra-violet (UV) photon at 358 nm via a cooperative energy transfer (CET) from Ce 3+ to Yb 3+ ions. Yb 3+ concentration dependent quantum efficiency has been calculated and the maximum efficiency approaches up to 175% before reaching the critical concentration quenching threshold. The development of NIR QC Ce 3+, Yb 3+ co-doped phosphors may open up a new approach to achieve high efficiency silicon-based solar cells by means of downconversion.

Quantum Cutting in Tm3+/Yb3+‐Codoped Lanthanum Aluminum Germanate Glasses

In the present paper, Tm3+/Yb3+‐codoped lanthanum aluminum germanate glasses are prepared by simply melting and quenching method. Quantum cutting (QC) between Tm3+ and Yb3+ ions in these samples is realized; in the QC process, one blue photon at about 467 nm is cut into two near‐infrared photons at about 1 μm. The maximum energy transfer efficiency and the corresponding QC efficiency can reach as high as 59.9% and 159.9%, respectively.

Infrared quantum-cutting analysis of Er0.3Gd0.7VO4 crystal for solar cell application

Recently the infrared quantum cutting has achieved an exciting development in enhancing the efficiency of solar cell. The infrared quantum cutting of Er0.3Gd0.7VO4 crystalline is studied in the present paper. It is found that the approximate quantum cutting efficiencies of 1532.5 nm 4I13/2→4I15/2 fluorescence, when the 2H11/2 and 4G11/2 levels are excited, are about 178.55% and 177.61% respectively. Especially, effective three-photon and four-photon infrared quantum cuttings of Er0.3Gd0.7VO4 crystalline excited by visible and near-violet light are found for the first time in the present paper. An interesting "peak - valley" conversion phenomenon in the excitation spectrum is also observed. It is also the first time for us to find the first-order infrared quantum cutting based single species Er3+ ion for Er0.3Gd0.7VO4 crystalline.

Near-infrared quantum cutting in RE 3+/Yb 3+ (RE = Pr, Tb, and Tm): GeO 2–B 2O 3–ZnO–LaF 3 glasses via downconversion

An efficient near-infrared (NIR) quantum cutting (QC) involving the emission of two near-infrared photons for each blue photon absorbed is realized in RE 3+/Yb 3+ (RE = Pr, Tb, and Tm): GeO 2–B 2O 3–ZnO–LaF 3 glasses. Upon excitation of Pr 3+, Tb 3+, and Tm 3+ ions with visible photons at 482, 483, and 467 nm two near-infrared photons at 950–1100 nm (Yb 3+: 2F 5/2 → 2F 7/2) through an efficient cooperative energy transfer from Pr 3+, Tb 3+, and Tm 3+ to Yb 3+, with an optimal quantum efficiency close to 200% has been demonstrated. The development of the near-infrared quantum cutting oxyfluoride glasses could open a route in achieving high efficiency silicon-based solar cells by means of downconversion in the visible part of the solar spectrum to ∼1000 nm photons with a two fold increase in the photon number.

UV photon harvesting and enhanced near-infrared emission in novel quantum cutting Ca2BO3Cl:Ce3+,Tb3+,Yb3+ phosphor

A novel near-infrared (NIR) quantum cutting (QC) Ca2BO3Cl:Ce3+,Tb3+,Yb3+ phosphor promising for luminescent solar concentrators (LSC) with Si solar cells was successfully developed. It can harvest UV photons and exhibits an intense NIR emission of Yb3+ around ∼1000 nm, perfectly matching the maximum spectral response of Si solar cells. The NIR emission intensity of Ca2BO3Cl:Ce3+,Tb3+,Yb3+ upon broadband excitation of Ce3+ ion at 288, 315 and 369 nm is about 9.1, 10 and 2.8 times as intense as that of GdBO3:Tb3+,Yb3+ with the highest NIR quantum efficiency of about 182% upon narrow excitation of Tb3+ ion at 488 nm. It demonstrates for the first time that Ce3+ ion can be an efficient sensitizer harvesting UV photons and greatly enhancing the NIR emission of Yb3+ ion through efficient energy feeding by the allowed 4f–5d absorption of Ce3+ ion with high oscillator strength. We believe this new NIR QC phosphor may open a new route to the design of advanced NIR QC phosphors for maximizing LSC performance with Si solar cells.

Cooperative downconversion in Y3Al5O12 : RE3+,Yb3+ (RE = Tb, Tm, and Pr) nanophosphors

Abstract— Efficient near‐infrared (NIR) quantum cutting (QC) through cooperative downconversion in Y3Al5O12 : RE3+,Yb3+ (RE = Tb, Tm, and Pr) nanophosphors has been demonstrated, which involves the conversion of the visible photon from RE3+ into the NIR emission of Yb3+ with the optimal quantum efficiency approaching 200%. The authors have analyzed the measured luminescence spectra and decay lifetimes and propose a mechanism to rationalize the NIR QC effect. The results indicate the potential of developing RE3+‐Yb3 dual‐ion‐based nanophosphors for the downconversion of high‐energy photons to multiple photons with an energy greater than the bandgap of silicon‐based‐photonics display devices.