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Mixed-anion compounds, in which multiple anions such as O2−, N3−, and H− are contained in the same compound, have recently attracted attention. Because mixed-anion compounds have a unique crystal s...

We synthesized luminescent coordination polymer glasses composed of d¹⁰ metal cyanides and triphenylphosphine through melt-quenching and mechanical milling protocols. Synchrotron X-ray total scattering measurements and solid-state NMR revealed their one-dimensional chain structures and high structural dynamics. Thermodynamic and photoluminescence properties were tunable by the combination of heterometallic ions (Ag⁺, Au⁺, and Cu⁺) in the structures. The glasses are moldable and thermally stable, and over centimeter-sized glass monoliths were fabricated by the hot-press technique. They showed high transparency over 80% from the visible to near-infrared region and strong green emission at room temperature. Furthermore, the glass-to-crystal transformation was demonstrated by laser irradiation through the photothermal effect of the glasses.

The five-fold square pyramid caused by Cl− introduction brings about an inconsistent energy shift of the charge transfer excited states.

Eu2+-Trapped exciton states in YSiO2N show anomalous deep-red to near-infrared luminescence under violet-blue light illumination.

Mixed-halide perovskites have attracted great attention in applications of lighting and photovoltaic devices due to their excellent properties. Understanding the phase segregation mechanism of mixed-halide perovskite has significance for suppressing the performance degradation of optoelectronic devices. Herein, we investigate the mixed-halide perovskite nanocrystals (NCs) in isolation from the external factors (oxygen, moisture, and pressure) using glass encapsulation, which shows excellent photostability against phase segregation. By monitoring the structural evolution of the NCs in glass matrices, the coexisting phase segregation and amorphization of mixed-halide perovskites are observed in real-time. The results show that thermal-induced local temperature increase plays a dominant role in the phase segregation of mixed-halide perovskite NCs. The recovery process is driven by the spontaneous crystallization of the amorphous mixed-halide phase. The clarified dynamic equilibrium process between the compositional segregation (mixing) and structural disorder (order) gives us a better insight into the reversible phase segregation mechanism of mixed-halide perovskite.

The objective of this work is to review and assess the potential of MgB4O7:Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of MgB4O7:Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al2O3:C, for example, MgB4O7:Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). MgB4O7:Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects.

The high-pressure structures of alkaline earth metal hydride-fluorides (AHFs) (A = Ca, Sr, Ba) were investigated up to 8 GPa. While AHF adopts the fluorite-type structure (Fm3[combining macron]m) at ambient pressure without anion ordering, the PbCl2-type (cotunnite-type) structure (Pnma) is formed by pressurization, with a declining trend of critical pressure as the ionic radius of the A2+ cation increases. In contrast to PbCl2-type LaHO and LaOF whose anions are fully ordered, the H-/F- anions in the high-pressure polymorph of SrHF and BaHF are partially ordered, with a preferential occupation of H- at the square-pyramidal site (vs. tetrahedral site). First-principles calculations partially support the preferential anion occupation and suggest occupation switching at higher pressure. These results provide a strategy for controlling the anion ordering and local structure in mixed-anion compounds.

A single-crystalline defect-less phosphor is desired for efficient luminescence of the therein doped optical activators. In this paper, microsized MgAl2O4:Mn4+ single-crystal phosphors with bright red luminescence were grown in molten LiCl salt at 950 °C, for application in blue LED pumped white lighting. By comparing the phosphor formation from various Mg2+- and Al3+-bearing sources, both the template-formation and the dissolution-diffusion processes were evidenced to account for the formation of the microsized MgAl2O4:Mn4+ crystallites. Using nano γ-Al2O3 as the Al3+-bearing precursor, the uniform MgAl2O4:Mn4+ microcrystallites with a {111} planes-exposed tetragonal bipyramid morphology were obtained. The photoluminescence property was studied at various temperatures, and Mg ↔ Al anti-site disorder induced luminescence broadening was discussed. The Mn4+ 2Eg → 4A2g transition in MgAl2O4 shows a quite short luminescence wavelength peaking at 651 nm and ultrabroadband emission extending to 850 nm. The luminescence is relatively robust against thermal effect with relatively high thermal quenching temperature of 400 K and activation energy of 0.23 eV. Employing the red-emitting MgAl2O4:Mn4+ crystallites, blue LED pumped white lighting prototypes were fabricated which simulate the solar-like spectrum and show neutral to warm white.

International audience; Co-doped hexagonal Sr1-x/2Al2-xSixO4:Eu 2+ ,Dy 3+ (0.1≤x≤0.5) transparent ceramics have been elaborated by full glass crystallization. The compositions with low SiO2 content (x≤0.4) require fast quenching conditions to form glass, i.e. specific elaboration processes such as aerodynamic levitation coupled to laser heating, whereas the x=0.5 glass composition can be prepared at large scale by classic meltquenching method in commercial furnaces. After a single thermal treatment, the resulting SrAl2O4-based transparent ceramics show varying photoluminescence emission properties when x increases. These variations are also observable in persistent luminescence, resulting in an afterglow colour-tuning ranging from green to light blue. Afterglow excitation spectra highlight the possible activation in the visible range of the obtained persistent luminescence. Indeed, persistent luminescence of hexagonal Sr0.75Al1.5Si0.5O4:Eu 2+ ,Dy 3+ large transparent ceramics has been successfully charged using a typical smartphone low power white light source. Moreover, thermoluminescence glow curves of samples containing different Dy 3+ doping concentrations are studied to gain insights regarding the traps origin and depth. Coupling thermoluminescence results together with luminescence thermal quenching and band gap calculations appears useful to understand the charge trapping and detrapping evolution with the material composition. Varying the Si-content in hexagonal Sr1-x/2Al2-xSixO4:Eu 2+ ,Dy 3+ compounds appears as a promising strategy to obtain transparent materials with tuneable green to light blue persistent luminescence.

Blue light pumped red luminescence with broadband and high photon-energy emission is highly desired for phosphor-converted white light-emitting diodes (pc-wLEDs), to achieve a high color rendering index and high luminous efficacy. Mn4+-doped red-emitting phosphors generally exhibit sharp vibronic emissions associated with the parity- and spin-forbidden 2Eg→4A2g transitions. In this paper, two abnormal luminescence behaviors were observed for Mn4+ in the MgAl2O4:Mn4+ spinel phosphor with a short wavelength emission band peaking at 651 nm. Firstly, the Mn4+ 2Eg→4A2g transition exhibits ultrabroadband luminescence in MgAl2O4 and the large full-width at half-maximum (FWHM) is dependent both on the calcination temperature and on the partial substitution of Al3+ with Ga3+. Secondly, the thermal quenching behavior of the Mn4+ 2Eg→4A2g luminescence in MgAl2O4 shows a dependence on its thermal treatment and preparation method. The Rietveld refinement and Raman results demonstrate that the variation in the FWHM of the luminescence spectra is a sum effect of structural ordering (i.e., isotropic displacement decrease of constituent atoms) and the Mg ↔ Al anti-site disorder. A model for the observed varying thermal quenching of luminescence was tentatively proposed. The intrinsic thermal quenching temperature of Mn4+ luminescence in MgAl2O4 was found to be 390-400 K using the samples prepared by the co-precipitation and molten salt methods. The present work gives a novel perspective to understand the luminescence spectra of Mn4+ 2Eg→4A2g transition.

The engineering of covalency and crystal field is a key point for the control of the 5d energy level of Eu2+. The hydride ion exhibits strong covalency, which results in a large 5d energy shift by the nephelauxetic effect compared to their fluoride analogues. In this study, the Eu2+-doped K2MgH4 Ruddlesden–Popper (n = 1) perovskite was prepared and its optical properties were investigated. Red luminescence due to the 4f65d1 → 4f7 transition was observed at 670 nm by UV excitation of the K2MgH4:Eu2+ sample. Compared with yellow Eu2+-luminescence at 565 nm of the KMgH3 cubic perovskite, which has almost the same chemical composition as K2MgH4, the additional red-shift of the luminescence in K2MgH4:Eu2+ is caused by the strong crystal field splitting in the unique 9-fold coordinated site in addition to the large nephelauxetic effect by hydride ions. Using a hydride model system that allows for a clear distinction between crystal field splitting and nephelauxetic effect, we successfully demonstrated the design concept for the 5d energy shifting by covalency and crystal field in Eu2+-doped K2MgH4. Also, the thermal quenching process of K2MgH4:Eu2+ by the ionization process was discussed in comparison to KMgH3:Eu2+ on the basis of the energy diagram.

Changing the electronic structure of materials by pressure and the accompanying changes in optical properties have attracted scientific interest. We have reported that the energy position of the conduction band (CB) bottom and the crystal field splitting of the Ce3+:5d excited level in Y3Al5−xGaxO12:Ce3+ are changed by applying pressure, which results in the red shifting of the Ce3+:5d → 4f luminescence and the increase of the quenching temperature. We also reported dramatic improvement of the persistent luminescence performance by either Cr3+ or Yb3+ codoping into the Y3Al5−xGaxO12:Ce3+ phosphors. The different trap depths formed by Cr3+ and Yb3+ affect the initial persistent luminescence intensity and the persistent luminescence duration. In this study, the effect of pressure on the persistent luminescence performance was investigated. For the Y3AlGa4O12:Ce3+–Yb3+ phosphor, the slope of persistent luminescence decay curve becomes more gentle with increasing pressure, while for the Y3AlGa4O12:Ce3+–Cr3+ phosphor the slope becomes steeper. These results indicate that the trap depth of Yb3+ becomes deeper and that of Cr3+ becomes shallower with increasing pressure. Based on the pressure-dependence of the luminescence quenching and the trap depth change estimated from the decay slopes, the relative electronic energies of the CB bottom and the Yb2+ (4f14) or Cr2+ (3d4) levels are discussed. The CB bottom energy is increased relative to the ground 1S0 state of Yb2+ with increasing pressure, which results in deepening of the electron trap depth of the Yb2+ state. The opposite tendency of the Cr3+ codoped sample was described by a decreasing tendency of the energy gap between the CB bottom and the Cr2+:eg level, the relative energy level of which is increased by the increase of the crystal field with increasing pressure in the garnet host material, where the electron-trapping Cr2+ ions take the high spin state (t32ge1g) rather than the low-spin state (t42g).

Glass matrix embedding is an efficient way to improve the chemical and thermal stability of the halide perovskite QDs. However, CsPbX

The photoluminescence properties of Cr

Orange persistent luminescence and photodarkening phenomena were observed after ultraviolet (UV) excitation in calcium-gallium-germanate (CGG) glass with a composition of 3CaO-1Ga2O3-3GeO2 prepared by a melt-quenching method. The CGG glass was characterized by using X-ray diffraction, differential scanning calorimetry, and Raman scattering analyses. Also, the optical and electronic properties of the CGG glass were investigated. Based on the electron paramagnetic resonance (EPR) spectra, it is found that new defects, NBOHC (nonbridging oxygen hole center) and E’(Ge) (unpaired electron at Ge ion bonding three oxygen), were created after UV excitation. From the good agreement between the time dependence of the photodarkening absorption intensity and EPR intensity of the NBOHC, the origin of the photodarkening phenomenon is found to be caused by NBOHC. Also, from the relationship between the time dependence of persistent luminescence intensity and the time-derivative EPR intensities of NBOHC and E’(Ge) center...

We report the synthesis and luminescence properties as well as band structure of a series of layered mixed-anion compounds, including a new layered mixed anion compound, Sr3Sc2Ag2Se2O5. The crystal structure, band structure, and optical properties of this new compound and of related compounds Sr3Sc2Cu2Ch2O5 (Ch:chalcogen = S, Se) are presented. The compounds have a common perovskite-like layer of (Sr3Sc2O5)2+ and different semiconductor layers of (Cu2S2)2−, (Cu2Se2)2− or (Ag2Se2)2−. Similar band structures are found for the valence band maximum (VBM), while the structure of the conduction band minimum (CBM) is different depending on the chalcogen species, resulting in the different band gap energies of the compounds. The band gap energies are estimated to be 3.3, 2.9, and 2.4 eV for Sr3Sc2Cu2S2O5, Sr3Sc2Cu2Se2O5, and Sr3Sc2Ag2Se2O5, respectively. Excitonic luminescence is observed near the band edge for all three compounds, with different wavelengths according to their band gap. These optical observations are consistent with the DFT calculations. The luminescence properties of the system can be controlled by changing the composition of the semiconductor-layers, thereby offering large flexibility in material design advantageous for various applications.

Eu2+-Dy3+ co-doped barium silicate glass was prepared by a melt quenching method and cerammed at various temperatures between 800 and 1250 °C to obtain the glass ceramic (GC) persistent phosphors. The crystal phase of Ba5Si8O21 was primarily precipitated in the GC samples. The GC sample cerammed at 1250 °C (GC1250) exhibited the longest persistent luminescence over 16 h until the luminance becomes 2 mcd/m2. The color of GC1250 sample was changed from white to blue after UV light illumination, and then bleached efficiently by red light (660 nm) illumination or heat treatment at 200 °C. From thermoluminescence (TL) glow curve measurements, four different TL glow peaks were observed at 191 K, 278 K, 446 K, and 494 K. On the other hand, after red-illumination following UV-illumination, the TL intensity of the only 446 K-peak was selectively decreased in the TL glow curve. It was shown that the blue photochromism of GC 1250 sample is due to an electron trapping defect strongly related with this glow peak.

The luminescence properties of Ce3+-doped GdxY3-xAl5-ySiyO12-yNy (x = 0, 1 and 2; y = 0.25) oxynitride garnet phosphors were investigated and compared with corresponding oxide garnet phosphors (y = 0). The measured photoluminescence spectra exhibit redshift of the emission peak wavelength by the partial nitridation of oxide garnet phosphors because of the strong crystal field splitting and the nephelauxetic effect. Temperature dependence studies of the photoluminescence intensity revealed that the quenching temperature decreased by partial nitridation and Gd substitution. The thermal activation energy, estimated from temperature dependence of the fluorescent lifetime, was found to decrease from 0.85 eV (x = 0, y = 0) to 0.27 eV (x = 2, y = 0.25).

Phosphors that emit in the deep-red spectral region are critical for plant cultivation light-emitting diodes. Herein, ultrabroadband deep-red luminescence of Mn4+ in La4Ti3O12 was studied, which showed intense zero phonon line emission. The double-perovskite structural La4Ti3O12 simultaneously contains two Ti4+ sites forming slightly- and highly-distorted TiO6 octahedra, respectively. The influence of octahedral distortion on the Mn4+ emission energy in the two distinct Ti4+ sites was studied both experimentally and theoretically. The spectral measurements indicated that Mn4+ in La4Ti3O12 showed intense zero phonon line emission (ZPL) at deep-red 710-740 nm under excitation of 400 nm charging the O2-→ Mn4+ charge transfer transition. The splitting of the ZPL of the Mn4+ 2Eg→4A2g transition as well as the intensity of ZPL relative to the vibronic phonon sideband emissions were found to be greatly influenced by the degree of octahedral distortion. The crystal-field strength and Racah parameters of Mn4+ in each Ti4+ site were also estimated. The Mn4+ 2Eg→4A2g luminescence exhibited severe thermal quenching, which was explained by the low-lying 4T2g level and charge-transfer state.

Great progress has been made in inorganic persistent phosphors, especially in the recent two decades, motivated by the discoveries of the SrAl2O4:Eu2+-Dy3+ in the green and Cr3+ doped spinel compounds in the deep-red to near-infrared (NIR) spectral regions. However, the physical mechanism behind this kind of “self-sustained” luminescence is still the subject of debate, and the improvement of known persistent phosphors and/or the development of new ones are still a matter of trial-and-error. In this review, starting from the introduction of longstanding histories of persistent luminescence (PersL), we provide comprehensive insights into its physical mechanism. Particular focus is put on the state-of-the-art of designing new persistent phosphors via “bandgap engineering”, based on the knowledge about trapping-detrapping mechanisms of charge carriers and energy level locations of emitting/trapping centers. Recent significant works on PersL observed in organic molecules and phosphorescence observed in inorganic phosphors are also highlighted in order to give a clear distinction between these two long-lived luminescence phenomena. Key challenges, feasible improvements and perspectives of PersL working in the ultraviolent (UV), white, red and NIR (over 1000 nm) regions together with new charging concepts by NIR or visible-light lasers are also presented. It is hoped that this review could give new inspiration for the future development of PersL in emerging applications.

The increasing attention on the unique properties of oxyhydride materials motivates the exploration of their potential applications in optical fields, and the theoretical studies of their luminescence properties are still under progress. Here, we report the experimental and theoretical high-pressure photoluminescence (PL) studies on Eu-activated Sr3– x AxAlO4H ( A = Ca and Ba; x = 0 and 1) oxyhydride materials. Under hydrostatic pressures from ambient pressure up to 6.41 GPa, the luminescence band in all the samples exhibits redshift with increasing pressure and the highest energy-shift rate of −101.85 cm−1/GPa was observed in Sr3AlO4H:Eu2+. The asymmetric bands were deconvoluted into two peaks corresponding to the two Eu sites with different coordination environments. Although the shift rates of Eu2+ centers in Sr3AlO4H are not remarkable as expected for the large compressibility of hydride ion ligands, their pressure-dependences in opposite directions were successfully reproduced by constrained density functional theory calculations using the advanced on-site Coulomb interaction parameter ( U) determination method. The lower shift rate as seen in conventional oxide phosphors indicates that Eu-4 f and 5 d level positions are determined by the interaction with less compressive oxide ion ligands. Therefore, the high shift rate required for pressure sensing applications is expected in more hydrogen-rich oxyhydrides and related hydride compounds.

Er3+/Dy3+ co-doped double-clad ZBLAN optical fiber has been used to obtain amplified spontaneous emission (ASE) broadband light sources cladding-pumped by 980-nm multimode laser diode (LD) sources. It has been demonstrated that mid-infrared broadband emission extending from 2515 to 3735 nm was obtained by energy transfer between Er3+ and Dy3+. We experimentally investigated the optimum design of Er3+/Dy3+ co-doped ZBLAN fiber in terms of ion concentration, fiber length, pumping configuration, and pumping power. The ASE output power was more than 2.5 mW when the LD pump power was set at 5 W. To assess its potential for gas sensing applications, the fabricated ASE light source was used to successfully detect methane gas with concentrations at 1% and 5%. The simple and stable construction of our ASE light source is suitable for practical purposes.

Understanding the role played by the material chemistry to increase the pressure sensitivity of new optical pressure probes is of great scientific interest. After almost 50 years from the first pro...

Mn4+ ions show red to deep-red luminescence due to the 2E→4A2 spin-forbidden transitions in several host materials. Especially, Mn4+-doped LaAlO3 with perovskite structure shows the deep red luminescence with a quite long wavelength around 730 nm in the first biological window. In this study, we investigated the temperature dependence of the photoluminescence spectra of Mn4+-Ca2+ co-doped LaAlO3 (LAP: Mn4+-Ca2+) and a possibility as a thermometer based on the energy shift of zero-phonon-line (ZPL) and the luminescence intensity ratio (LIR) of thermally coupled ZPL and anti-Stokes phonon sideband (PSB). As a result, the LAP: Mn4+-Ca2+ phosphor shows the continuous energy shift of ZPL with temperature and three different temperature dependences of the LIR by selecting different two luminescence bands, which means that the LAP: Mn4+-Ca2+ phosphor has four different thermometric functions in one phosphor. All the thermometers show a good relative sensitivity and wide working temperature range from 100 K to physiological temperature.

A single-crystalline defect-less phosphor is desired for efficient luminescence of the therein doped optical activators. In this paper, microsized MgAl

Co-doped hexagonal Sr1-x/2Al2-xSixO4:Eu2+,Dy3+ (0.1 ≤ x ≤ 0.5) transparent ceramics have been elaborated by full glass crystallization. The compositions with low SiO2 content (x ≤ 0.4) require fast quenching conditions to form glass, i.e. specific elaboration processes such as aerodynamic levitation coupled to laser heating, whereas the x = 0.5 glass composition can be prepared on a large scale by the classic melt-quenching method in commercial furnaces. After a single thermal treatment, the resulting SrAl2O4-based transparent ceramics show varying photoluminescence emission properties when x increases. These variations are also observable in persistent luminescence, resulting in an afterglow colour-tuning ranging from green to light blue. Afterglow excitation spectra highlight the possible activation in the visible range of the obtained persistent luminescence. Indeed, persistent luminescence of hexagonal Sr0.75Al1.5Si0.5O4:Eu2+,Dy3+ large transparent ceramics has been successfully charged using a typical smartphone low power white light source. Moreover, thermoluminescence glow curves of samples containing different Dy3+ doping concentrations are studied to gain insights regarding the traps' origin and depth. Coupling thermoluminescence results together with luminescence thermal quenching and band gap calculations appear useful to understand the charge trapping and detrapping evolution with the material composition. Varying the Si-content in hexagonal Sr1-x/2Al2-xSixO4:Eu2+,Dy3+ compounds appears as a promising strategy to obtain transparent materials with tuneable green to light blue persistent luminescence.

Luminescence Boltzmann thermometry is one of the most reliable techniques used to locally probe temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based

Changing the electronic structure of materials by pressure and the accompanying changes in optical properties have attracted scientific interest. We have reported that the energy position of the conduction band (CB) bottom and the crystal field splitting of the Ce3+:5d excited level in Y3Al5-xGaxO12:Ce3+ are changed by applying pressure, which results in the red shifting of the Ce3+:5d → 4f luminescence and the increase of the quenching temperature. We also reported dramatic improvement of the persistent luminescence performance by either Cr3+ or Yb3+ codoping into the Y3Al5-xGaxO12:Ce3+ phosphors. The different trap depths formed by Cr3+ and Yb3+ affect the initial persistent luminescence intensity and the persistent luminescence duration. In this study, the effect of pressure on the persistent luminescence performance was investigated. For the Y3AlGa4O12:Ce3+-Yb3+ phosphor, the slope of persistent luminescence decay curve becomes more gentle with increasing pressure, while for the Y3AlGa4O12:Ce3+-Cr3+ phosphor the slope becomes steeper. These results indicate that the trap depth of Yb3+ becomes deeper and that of Cr3+ becomes shallower with increasing pressure. Based on the pressure-dependence of the luminescence quenching and the trap depth change estimated from the decay slopes, the relative electronic energies of the CB bottom and the Yb2+ (4f14) or Cr2+ (3d4) levels are discussed. The CB bottom energy is increased relative to the ground 1S0 state of Yb2+ with increasing pressure, which results in deepening of the electron trap depth of the Yb2+ state. The opposite tendency of the Cr3+ codoped sample was described by a decreasing tendency of the energy gap between the CB bottom and the Cr2+:eg level, the relative energy level of which is increased by the increase of the crystal field with increasing pressure in the garnet host material, where the electron-trapping Cr2+ ions take the high spin state (t32ge1g) rather than the low-spin state (t42g).

We have developed a novel persistent phosphor of LaAlO

Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochemistry of 6s

Luminescence Boltzmann thermometry is one of the most reliable techniques used to locally probe temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based 4T2 → 4A2/2E → 4A2 emission ratio of Cr3+. On the basis of structural information of the local HfO6 octahedral site we demonstrated the potential of the CaHfO3:Cr3+ system by combining deep theoretical and experimental investigation. The material exhibits simultaneous emission from both the 2E and 4T2 excited states, following the Boltzmann law in a cryogenic temperature range of 40-150 K. The promising thermometric performance corroborates the potential of CaHfO3:Cr3+ as a Boltzmann cryothermometer, being characterized by a high relative sensitivity (∼ 2%·K-1 at 40 K) and exceptional thermal resolution (0.045-0.77 K in the 40-150 K range). Moreover, by exploiting the flexibility of the 4T2-2E energy gap controlled by the crystal field of the local octahedral site, the design proposed herein could be expanded to develop new Cr3+-doped cryogenic thermometers.

The spectral mismatch between the solar spectrum and the sensitivity curve of crystalline silicon (c-Si) solar cell limits energy conversion efficiency of the solar cell. The energy conversion efficiency had approached the Shockley–Queisser's limit, theoretical conversion efficiency of c-Si, of 30%. Luminescent converters, which are expected to show the ideal quantum cutting, have been studied because they have potential to improve c-Si solar cell efficiency up to 38.6%. In this chapter, Yb3+ and lanthanide ion (Ce3+, Pr3+, Nd3+, Eu2+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+) co-doped wavelength converters for c-Si solar cell and their UV/blue to 1 μm downconversion processes are described.

The development of nanomaterials with high sensitivity to external stimuli such as temperature is critical to investigate the driving force of not only biological processes but also catalytic mecha...