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Novel emission bands of Na2TiF6:Mn4+ phosphors induced by the cation exchange method
摘要： A series of Na2TiF6:xMn4+ samples were prepared by the cation exchange method. Visible QC behavior and the strongest ZPL peaks were observed for these samples. The characteristic of the visible QC behavior is that PL intensity at 620 nm is 1.61 times as high as PLE intensity at 476 nm. The mechanisms of these phenomena were discussed, and the color purity, crystal-field and nephelauxetic effect, the critical distance and the multipolar interaction for the samples were determined. The result shows that the Mn4+ ions are located at a strong crystal field and the concentration quenching of Mn4+ is from the quadrupole-quadrupole interaction. The slightly increase of nephelauxetic ratio causes the slightly blue shift of emission. The color-purity and chromaticity coordinates of the optimal sample suggests that the strongest ZPL makes its red emission with high color-purity. Thus, Na2TiF6:0.08Mn4+ is a potential red-emitting phosphor for blue light-based WLEDs.
关键词： Fluorides,Photoluminescence,Mn4+,Red emitting phosphor,Visible quantum cutting
更新于2025-09-23 15:23:52
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Near-infrared quantum cutting via energy transfer in Bi3+, Yb3+ co-doped Lu2GeO5 down-converting phosphor
摘要： In recent years, down-converting phosphors have grown rapidly and been still growing for their potential to significantly improve the photoelectric conversion efficiency of silicon-based solar cells. However, the discovery of new optical materials with optimized properties (in terms of emission intensity, chemical and thermal stability and quantum yield) would still be of the utmost importance. Herein, we report a novel down-converting phosphor Lu2GeO5: Bi3+, Yb3+. Our research results show that the energy transfer efficiency from Bi3+ to Yb3+ in Lu2GeO5 is as high as 65%. Via such an energy transfer from Bi3+ to Yb3+, an absorbed ultraviolet photon gives rise to almost two emitted infrared photons. The theoretical quantum yield of Lu2GeO5: Bi3+, Yb3+ system is calculated to reach up to 165%. The mechanism of the energy transfer from Bi3+ to Yb3+ is proved to be an electric dipole-dipole interaction. Meanwhile, Lu1.87GeO5: 0.03Bi3+, 0.10 Yb3+ phosphor exhibits an excellent resistance against thermal quenching. The present investigation provides people a new down-converting phosphor Bi3+, Yb3+ co-doped Lu2GeO5 with near-infrared quantum cutting to achieve high photoelectric conversion efficiency of silicon-based solar cells.
关键词： Lu2GeO5: Bi3+, Yb3+,Quantum cutting,Energy transfer,Down-converting phosphors
更新于2025-09-23 15:23:52
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Three-photon near-infrared quantum cutting in β-NaGdF4:Yb3+
摘要： Three-photon near-infrared quantum cutting of Gd3+ to Yb3+ was observed in b-NaGdF4:Yb3+ for the first time. The consistency between theoretical predictions by applying rate equations in the quantum cutting model and experimental results obtained from fluorescence spectra successfully confirmed the occurrence of three-photon near-infrared quantum cutting. The strong interaction between Yb3+ ions is a key factor affecting energy transfer. Maximum energy transfer efficiency and the quantum efficiency can reach 98.2% and 296.5%, respectively. High-efficiency three-photon near-infrared quantum cutting has an admirably promising application prospect in improving the photoelectric conversion efficiency of c-Si solar cells.
关键词： Near-infrared quantum cutting,b-NaGdF4,Three-photon
更新于2025-09-23 15:22:29
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On the Mechanism for the Extremely Efficient Sensitization of Yb3+ Luminescence in CsPbCl3 Nanocrystals
摘要： Rare earth (RE3+) doped inorganic CsPbX3 (X=Cl or Cl/Br) nanocrystals have been presented as promising materials for applications in solar-energy-conversion technology. An extremely efficient sensitization of Yb3+ luminescence in CsPbCl3 nanoparticles (NCs) was very recently demonstrated where quantum cutting is responsible for photoluminescence quantum yields over 100% (T. J. Milstein, et al., Nano Letters 2018, 18, 3792). In the present work, based on cubic phase of inorganic perovskite, we seek atom-level-insight into the basic mechanisms behind these observations in order to boost the further development of RE3+ doped CsPbX3 NCs for optoelectronics. In our calculations of cubic crystal structure, we do not find any energy level formed in the middle of the band gap, which disfavors a mechanism of step-wise energy transfer from the perovskite host to two Yb3+ ions. Our work indicates that the configuration with 'right-angle' Yb3+-VPb-Yb3+ couple are most likely to form in Yb3+-doped CsPbCl3. Associated with this 'right-angle' couple, the 'right-angle' Pb atom with trapped excited states would localize the photogenerated electrons and could act as the energy donor in a quantum cutting process, which achieves simultaneous sensitization of two neighboring Yb3+ ions.
关键词： Quantum cutting,Ytterbium-Doped inorganic perovskite,density function theory (DFT)
更新于2025-09-23 15:22:29
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Anion Exchange and the Quantum-Cutting Energy Threshold in Ytterbium-Doped CsPb(Cl1-xBrx)3 Perovskite Nanocrystals
摘要： Colloidal halide perovskite nanocrystals of CsPbCl3 doped with Yb3+ have demonstrated remarkably high sensitized photoluminescence quantum yields (PLQYs), approaching 200%, attributed to a picosecond quantum-cutting process in which one photon absorbed by the nanocrystal generates two photons emitted by the Yb3+ dopants. This quantum-cutting process is thought to involve a charge-neutral defect cluster within the nanocrystal's internal volume. Here, we demonstrate that Yb3+-doped CsPbCl3 nanocrystals can be converted post-synthetically to Yb3+-doped CsPb(Cl1-xBrx)3 nanocrystals without compromising the desired high PLQYs. Nanocrystal energy gaps can be tuned continuously from Eg ~ 3.06 eV (405 nm) in CsPbCl3 down to Eg ~ 2.53 eV (~490 nm) in CsPb(Cl0.25Br0.75)3 while retaining a constant PLQY above 100%. Reducing Eg further causes a rapid drop in PLQY, interpreted as reflecting an energy threshold for quantum cutting at approximately twice the energy of the Yb3+ 2F7/2 → 2F5/2 absorption threshold. These data demonstrate that very high quantum-cutting energy efficiencies can be achieved in Yb3+-doped CsPb(Cl1-xBrx)3 nanocrystals, offering the possibility to circumvent thermalization losses in conventional solar technologies. The presence of water during anion exchange is found to have a deleterious effect on the Yb3+ PLQYs but does not affect the nanocrystal shapes, morphologies, or even reduce the excitonic PLQYs of analogous undoped CsPb(Cl1-xBrx)3 nanocrystals. These results provide valuable information relevant to development and application of these unique materials for spectral-shifting solar energy conversion technologies.
关键词： ytterbium doping,quantum cutting,anion exchange,Perovskite nanocrystals
更新于2025-09-19 17:15:36
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Effects of La3+ on the enhancement NIR quantum cutting and UC emissions in Nd3+–Yb3+ co-doped transparent silicate glass-ceramics for solar cells
摘要： Near-infrared (NIR) quantum cutting (QC) and upconversion (UC) emission of Nd3+–Yb3+ co-doped in Si–Al–Ba–La transparent silicate glass-ceramics (SGC) were prepared. Influence of La3+ on the enhancement NIR QC and UC emission intensity of the co-doped Nd3+–Yb3+ in SGC were investigated. Thereby, NIR QC and UC emission intensity of the co-doped Nd3+–Yb3+ were increased strongly with increasing concentration of LaF3 from 5 up to 25 mol. %. The value of NIR QC emission intensity of the co-doped Nd3+–Yb3+ band centered at ~890, 947, 1071, 1339 and 1430 nm is maximized when the concentration of LaF3 reaches 25 mol. %. At the same time, with the increasing concentration of Yb3+, NIR QC emission intensity of the co-doped Nd3+–Yb3+ bands centered at ~890, 1071, 1339 and 1430 nm of Nd3+ and 947 nm of Yb3+ were gradually increased and reaches its maximum at 2.5 mol. % Yb3+, then decreased owing to the self-quenching effect. In addition, NIR QC mechanism and energy transfer (ET) processes between 2F5/2 → 2F7/2 transition of Yb3+ and transitions of Nd3+ are discussed.
关键词： Solar cells,Upconversion,Near-infrared quantum cutting,Nd3+–Yb3+ co-doped
更新于2025-09-16 10:30:52
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Impact of Host Composition, Co-doping or Tri-doping on Quantum Cutting Emission of Ytterbium in Halide Perovskite Quantum Dots and Solar Cells Applications
摘要： Recently, various lanthanide ions (Ln3+) have been successfully doped into perovskite quantum dots (PQDs) and quantum-cutting emission of 2F5/2-2F7/2 for Yb3+with measurable inner efficiency more than 100 % has been discovered, applied as the luminescent converter of solar cells, which has opened a new branch for the application of PQDs. In this work, to further improve the quantum-cutting efficiency of Yb3+, the co-doping and tri-doping methods were displayed to improve the quantum cutting emission of PQDs. The Yb3+-Ln3+ (Ln=Nd, Dy, Tb, Pr, Ce) pairs doped CsPbClxBryI3-x-y PQDs were fabricated, which all displayed excitonic emissions, narrow-band emission of Ln3+ ions and quantum cutting emission of Yb3+ ions. It was interesting to observe that Yb3+-Pr3+ as well as Yb3+-Ce3+ pairs could effectively sensitize the emission of Yb3+, owing to Pr3+ and Ce3+ ions offered intermediate energy states close to the exciton transition energy of the PQDs. After host composition optimization and tri-doping investigation, overall emissions with 173% photoluminescence quantum yield (PLQY) were obtained in the Yb3+-Pr3+-Ce3+ tri-doped CsPbClBr2 PQDs. Then, the tri-doped PQDs was designed as the down-converter for the CuIn1-xGaxSe2 (CIGS) as well as the silicon solar cells, which relatively leads to enhancement of power conversion efficiency (PCE) as high as ～ 20%. The modified CIGS was further employed to charging the smart mobile phone, which could largely shorten the charging time from 180 to 150 min. This finding is of great significant for expanding the application fields of the impurity doped PQDs.
关键词： CIGS solar cell,ytterbium doping,quantum cutting,tri-doping method,Perovskite quantum dot
更新于2025-09-11 14:15:04
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Quantum cutting properties of Tb3+/Yb3+ co-doped ZrO2-SiO2 nano-crystalized glasses synthesized via a sol-gel route
摘要： Tb3+/Yb3+ co-doped ZrO2-SiO2 nano-crystallized glasses were prepared by a sol-gel process. The crystal structure and optical properties including down-conversion photoluminescence (or, quantum cutting) of the Tb3+-Yb3+ system with respect to gel heat treatment temperature were investigated by X-ray diffraction (XRD), Raman, photoluminescence (PL), and PL decay curves analysis. The energy transfer efficiency from Tb3+ to Yb3+ ions, which converts one photon to two photons with lower energy, increased with heat-treatment temperature. Furthermore, the oxidation state of Tb4+ ions was suspected to influence the emission intensity of Tb3+ and energy conversion efficiency. Thus, a post-treatment reduction was applied to the sample heated at 1100 oC by annealing it at 1100 oC for 1 h under 5%H2/95%N2 reductive atmosphere. Consequently, the thermodynamically generated Tb4+ ions were reduced to a trivalent state, leading to higher energy transfer efficiency.
关键词： ZrO2 nanocrystals,Sol-gel method,photoluminescence,quantum cutting,Tb3+-Yb3+ pair,Tb4+ ions
更新于2025-09-09 09:28:46
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Quantum Cutting Luminescent Solar Concentrators Using Ytterbium Doped Perovskite Nanocrystals
摘要： We introduce and demonstrate the concept of quantum-cutting luminescent solar concentrators (QC-LSCs) using Yb3+-doped perovskite nanocrystals. These NCs feature a photoluminescence quantum yield approaching 200% and virtually zero self-absorption loss of PL photons, defining a new upper limit of 150% for the internal optical efficiency (ηint) of LSCs that is almost independent of LSC sizes. An unoptimized 25 cm2 QC-LSC fabricated from Yb3+-doped CsPbCl3 NCs already displayed an ηint of 118.1±6.7% that is 2-fold higher than previous records using Mn2+-doped quantum dots (QDs). If using CsPbClxBr3-x NCs capable of absorbing ~7.6% of solar photons, the projected external optical efficiency (ηext) of QC-LSCs can exceed 10% for >100 cm2 devices which still remains a big challenge in the field. The advantage of QC-LSCs over conventional QD-LSCs becomes especially obvious with increasing LSC sizes, which is predicted to exhibit more than 4-fold efficiency enhancement in the case of window size (1 m2) devices.
关键词： Luminescent solar concentrators,Solar energy,Doped nanocrystals,Quantum cutting,Ytterbium doping
更新于2025-09-04 15:30:14