Improving the NIR light‐harvesting of perovskite solar cell with upconversion fluorotellurite glass

Upconversion glasses are capable of converting the sub‐bandgap NIR light into photons of a particular wavelength which can be efficiently utilized by solar cells. Herein, the Yb³⁺/Er³⁺ co‐doped fluorotellurite upconversion glasses were prepared. The most intense upconversion luminescence (UCL) under 980‐nm LD excitation was obtained in the glass with Yb³⁺‐to‐Er³⁺ molar ratio of 10:1. The dependences of UCL on the pump power and temperature were investigated. The UCL can be mainly attributed to the two‐photon involved energy transfer processes and is very stable to the change in temperature even when heated up to 200°C. The subsequent implementation of the glass as upconverter for a MAPbI_3‐xCl_x‐based perovskite solar cell (PSC) resulted in an open circuit voltage of 0.83 V and a short circuit current density of 0.32 mA/cm². This application of upconversion glass for enhancing the NIR light harvesting offers a promising way to improve the photo‐electric conversion efficiencies of PSCs.     

Structural,optical, and spectroscopic properties of Er3+-doped TeO2–ZnO–ZnF2 glass-ceramics

Transparent fluorotellurite glass-ceramics have been obtained by heat treatment of precursor Er-doped TeO₂–ZnO–ZnF₂ glasses. ErF₃ nanocrystals nucleated in the glass-ceramics have a typical size of 45 ± 10 nm. Based on the Judd-Ofelt theory, the main radiative parameters for the ⁴I_13/2 → ⁴I_15/2 transition have been obtained. The split of the absorption and emission bands and the reduction of the Ω₂ parameter, as compared to the glass, confirm the presence of Er³⁺ ions in a crystalline environment in glass-ceramic samples. The analysis of the ⁴I_13/2 decays suggests that a fraction of Er³⁺ ions remains in a glass environment while the rest forms nanocrystals. For the glass-ceramics, intense red and green upconversion emissions were observed with an enhancement of the ⁴F_9/2 → ⁴I_15/2 red one compared to the glass sample. The temporal evolution of the red emission together with the excitation upconversion spectra suggests that energy transfer processes are responsible for the enhancement of the red emission.     

Effect of BaF2 Content on Luminescence of Rare‐Earth Ions in Borate and Germanate Glasses

Rare‐earth‐doped oxyfluoride germanate and borate glasses were synthesized and next studied using spectroscopic methods. Influence of fluoride modifier on luminescence properties of rare earths in different glass hosts was examined. The excitation and emission spectra of Pr³⁺ and Er³⁺ ions in the studied glasses were registered. The emission spectra of Pr³⁺ ions in germanate and borate glasses are quite different and depend strongly on the glass host. In samples doped with Er³⁺ ions emission bands located around 1530 nm corresponding to the main ⁴I_13/2→⁴I_15/2 laser transition were registered, independently of the glass host. Quite long‐lived near‐infrared luminescence of Er³⁺ ions was observed for germanate glasses with low BaF₂ content, while in borate glass systems influence of barium fluoride on luminescence lifetimes is not so evident. The Judd–Ofelt calculations were used in order to determine quantum efficiencies of excited states of rare‐earth ions in germanate and borate glasses.     

Optimization of sensitizer concentration for upconversion photoluminescence of Yb3+/Er3+: La10W22O81 nanophosphor rods

Yb³⁺/Er³⁺codoped La₁₀W₂₂O₈₁ (LWO) nanophosphor rods have been successfully synthesized by a facile hydrothermal assisted solid state reaction method, and their upconversion photoluminescence properties were systematically studied. X-ray diffraction patterns revealed that the nanophosphors have an orthorhombic structure with space group Pbcn (60). A microflowers-like morphology with irregular hexagonal nanorods was observed using field emission scanning electron microscopy for the Yb³⁺(2 mol%)/Er³⁺(2 mol%):LWO nanophosphor. The shape and size of the nanophosphor and the elements along with their ionic states in the material were confirmed by TEM and XPS studies, respectively. A green upconversion emission was observed in the Er³⁺: LWO nanophosphors under 980 nm laser excitation. A significant improvement in upconversion emission has been observed in the Er³⁺: LWO nanophosphors by increasing the Er³⁺ ion concentration. A decrease in the upconversion emission occurred due to concentration quenching when the doping concentration of Er³⁺ ions was greater than 2 mol%. An optimized Er³⁺(2 mol%): LWO nanophosphor exhibited a strong near infrared emission at 1.53 μm by 980 nm excitation. The green upconversion emission of Er³⁺(2 mol%): LWO was remarkably enhanced by co-doping with Yb³⁺ ions under 980 nm excitation because of energy transfer from Yb³⁺ to Er³⁺. The naked eye observed this upconversion emission when co-doping with 2 mol% Yb³⁺. In order to obtain the high upconversion green emission, the optimized sensitizer concentration of Yb³⁺ ions was found to be 2 mol%. The upconversion emission trends were studied as a function of stimulating laser power for an optimized sample. Moreover, the NIR emission intensity has also been enhanced by co-doping with Yb³⁺ ions due to energy transfer from Yb³⁺ to Er³⁺. The energy transfer dynamics were systematically elucidated by energy level scheme. Colorimetric coordinates were determined for Er³⁺ and Yb³⁺/Er³⁺: LWO nanophosphors. The energy transfer mechanism was well explained and substantiated by several fluorescence dynamics of upconversion emission spectra and CIE coordinates. The results demonstrated that the co-doped Yb³⁺(2 mol%)/Er³⁺(2 mol%): LWO nanophosphor material is found to be a suitable candidate for the novel upconversion photonic devices.     

1.53 µm luminescence properties of Er3+-doped K–Sr–Al phosphate glasses

Trivalent erbium (Er³⁺)-doped K–Sr–Al phosphate glasses were prepared and studied their spectroscopic properties as a function of Er₂O₃ concentration. Judd–Ofelt analysis has been carried out for 1.0 mol% Er₂O₃-doped phosphate glass and in turn radiative properties have been evaluated for the excited levels of Er³⁺ ion. The radiative lifetime for the ⁴I_13/2 level was found to be higher for the present glass when compared to other Er³⁺-doped glasses. The Er³⁺-doped glasses exhibit intense near infrared emission at 1.53 µm corresponds to ⁴I_13/2→⁴I_15/2 transition as well as green emission at 546 nm corresponding to ⁴S_3/2→⁴I_15/2 under 980 nm and 488 nm excitations, respectively. The emission cross-section spectrum for 1.0 mol% of Er₂O₃-doped glass has been evaluated using McCumber theory. The gain cross-section has been evaluated as a function of population inversion, which revealed that the lasing action would be achieved at 1.53 µm for a population inversion about 40%. Decay curves for the ⁴I_13/2 level were measured and lifetimes have been determined for the studied glasses. The results indicate that the present glasses could be useful for laser as well as optical amplifiers at 1.53 µm.     

Upconverting luminescence based dual-modal temperature sensing for Yb3+/Er3+/Tm3+: YF3 nanocrystals embedded glass ceramic

Yb³⁺/Er³⁺/Tm³⁺ doped transparent glass ceramic containing orthorhombic YF₃ nanoparticles was successfully synthesized by a melt-quenching method. After glass crystallization, tremendously enhanced (about 5000 times) upconversion luminescence, obvious Start-splitting of emission bands as well as long upconversion lifetimes of Er³⁺/Tm³⁺ confirmed the incorporation of lanthanide activators into precipitated YF₃ crystalline environment with low phonon energy. Furthermore, temperature-dependent upconversion luminescence behaviors of glass ceramic were systematically investigated to explore its possible application as optical thermometric medium. Impressively, both fluorescence intensity ratio of Er³⁺: ²H_11/2 → ⁴I_15/2 transition to Er³⁺: ⁴S_3/2 → ⁴I_15/2 one and fluorescence intensity ratio of Tm³⁺: ³F_2,3 → ³H₆ transition to the combined Tm³⁺: ¹G₄ → ³F₄/Er³⁺: ⁴F_9/2 → ⁴I_15/2 ones were demonstrated to be applicable as temperature probes, enabling dual-modal temperature sensing. Finally, the thermal effect induced by the irradiation of 980 nm laser was found to be negligible in the glass ceramic sample, being beneficial to gain intense and precise probing signal and detect temperature accurately.     

Efficient near-infrared to visible and ultraviolet upconversion in polycrystalline BiOCl:Er3+/Yb3+ synthesized at low temperature

Er³⁺/Yb³⁺ co-doped BiOCl poly-crystals were synthesized by the conventional solid state method at 500 °C, which exhibited good crystalline and low phonon energy. Under 980 nm excitation, the samples showed intense red upconversion (UC) luminescence (Er³⁺: ⁴F_9/2→⁴I_15/2) as well as other four UC emission bands, including ultraviolet (UV) emission at 380 nm, violet emission at 411 nm, green UC emissions at 525 and 545 nm and near-infrared (NIR) emission between 800 and 850 nm, corresponding to the transitions of ⁴G_11/2, ²H_9/2, ²H_11/2, ⁴S_3/2 and ⁴I_9/2→⁴I_15/2 of Er³⁺, respectively. Interestingly, including the violet and green UC emissions, the red one originated a nearly three-photon process in this system, and a possible UC mechanism was proposed for the enhanced red emission.     

Intense 2.7 µm emission of Er3+/Pr3+ doped Ga5Ge20Sb10S65 chalcogenide glass

There are numerous vital usages for mid-infrared (MIR) lasers in satellite communication, biomedicine, military, remote sensing, and environmental monitoring. In this work, a progression of Er³⁺ ions doped, Er³⁺/Pr³⁺ ions co-doped Ga₅Ge₂₀Sb₁₀S₆₅ glasses were prepared, and their physical performances and structural characteristics were examined. To understand the non-phonon-assisted energy transfer mechanism, we recorded the up-conversion and infrared fluorescence emission spectra by pumping with a commercial 980 nm LD. Then the 2.7 µm strong fluorescence signal intensity can be obtained when the doped concentration of Pr³⁺ is proper. After the doping of Pr³⁺, fluorescence lifetime results revealed that the lifetimes of the Er³⁺:⁴I_13/2 level fell dramatically from 7.33 to 1.90 ms, which experienced a much more significant decrease in lifetimes than the Er³⁺:⁴I_11/2 level. The MIR fluorescence performances were assessed by the determined J–O parameters and relative emission cross sections. Additionally, the generally huge emission cross sections and the small pump energy show that it is possible to obtain population inversion with relatively small pump energy; thus the Er³⁺/Pr³⁺ glasses have great potential to be 2.7 µm laser materials.     

Ce3+ induced broadband enhancement around 2 μm in Tm3+/Ho3+ co-doped tellurite glass

Tellurite glasses doped with Tm³⁺, Ho³⁺ and Ce³⁺ ions were prepared via melt-quenching to realise broadband and fluorescence enhancement in near-infrared (NIR) band. Under the pumping of a commercial 808 nm laser diode (LD), the emission bands at 2.0 μm, 1.85 μm, 1.47 μm, and 705 nm were observed in the Tm³⁺/Ho³⁺ co-doping glass samples, which originated from the transitions of Ho³⁺:⁵I₇→⁵I₈ and Tm³⁺:³F₄→³H₆, ³H₄→³F₄, ³F_2,3 → ³H₆, respectively. The existence of 2.0 μm band fluorescence is due to the energy transfer from the Tm³⁺:³F₄ level to the Ho³⁺:⁵I₇ level. This band overlaps with the 1.85 μm band which forms a broadband fluorescence spectrum in the range of 1600–2200 nm. In glass samples co-doped with Tm³⁺/Ho³⁺ with 0.085 mol% Ho₂O₃ and 1 mol% Tm₂O₃, the full width at half maximum (FWHM) of this broadband spectrum (1600–2200 nm) was as high as ∼370 nm. After introducing 0.6 mol% CeO₂, the emission intensity of broadband fluorescence increased by ∼50%, which was caused by the cross-relaxations between Ce³⁺ and Tm³⁺ ions. The lifetime of fluorescence decay was determined to prove the interactions among the doped rare-earth ions, the radiative parameters such as transition probability, branching ratio and radiative lifetime were calculated from the absorption spectra based on the Judd-Ofelt theory to better understand the observed luminescence phenomena. In addition, X-ray diffraction (XRD) confirmed the amorphous state structure of the synthesised glass samples, while Raman spectrum revealed the different vibrational structural units forming the glass network.     

Enhancement of up-conversion emission and emerging cool white light emission in co-doped Yb3+/ Er3+: Li2O-LiF-B2O3-ZnO glasses for photonic applications

A series of co-doped (Yb³⁺/Er³⁺): Li₂O-LiF-B₂O₃-ZnO glasses were prepared by standard melt quenching technique. Structural and morphological studies were carried out by XRD and FESEM. Phonon energy dynamics have been clearly elucidated by Laser Raman analysis. The pertinent absorption bands were observed in optical absorption spectra of singly doped and co-doped Yb³⁺/Er³⁺: LBZ glasses. We have been observed a strong up-conversion red emission pertaining to Er³⁺ ions at 1.0 mol% under the excitation of 980 nm. However, the up-conversion and down conversion (1.53 µm) emission intensities were remarkably enhanced with the addition of Yb³⁺ ions to Er³⁺: LBZ glasses due to energy transfer from Yb³⁺ to Er³⁺. Up-conversion emission spectra of co-doped (Yb³⁺/Er³⁺): LBZ glasses exhibits three strong emissions at 480 nm, 541 nm and 610 nm which are assigned with corresponding electronic transitions of ²H_9/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 respectively. Consequently, the green to red ratio values (G/R) also supports the strong up-conversion emission. The Commission International de E′clairage coordinates and correlated color temperatures (CCT) were calculated from their up-conversion emission spectra of co-doped (Yb³⁺/Er³⁺): LBZ glasses. The obtained chromaticity coordinates for optimized glass (0.332, 0.337) with CCT value at 5520 K are very close to the standard white colorimetric point in cool white region. These results could be suggested that the obtained co-doped (Yb³⁺/Er³⁺): LBZ glasses are promising candidates for w-LEDs applications.     

Glass-forming regions and enhanced 2.7 μm emission by Er3+ heavily doping in TeO2–Ga2O3–R2O (or MO) glasses

Er³⁺-doped fiber lasers operating at 2.7 μm have attracted increasing interest because of their various important applications; however, the intrinsic self-terminating effect of Er³⁺ and the reliability of glass hosts hindered the development of Er³⁺-doped fiber lasers. Herein, the glass-forming regions of a series TeO₂–Ga₂O₃–R₂O (or MO) (R = Li, Na, and Rb; M = Mg, Sr, Ba, Pb, and Zn) glasses are predicted by the thermodynamic calculation method. On this basis, the physical and optical properties of TeO₂–Ga₂O₃–ZnO (TGZ) glass are investigated in detail as an example. Under the excitation of 980 nm laser diode, the fluorescence intensity at 2.7 μm reaches a maximum in the heavily Er³⁺-doped TGZ glass. By contrast, the accompanying near-infrared fluorescence at 1.5 μm and upconversion green emissions at 528 nm and 546 nm are all effectively weaken. Furthermore, the lifetime gap between the ⁴I_11/2 upper laser level and ⁴I_13/2 lower laser level is sharply narrowed from 2.81 ms to 0.59 ms, which is beneficial to overcome the population conversion bottleneck. All results demonstrate that these newly developed ternary tellurite glass systems are promising candidates for near-/mid-infrared laser glass fiber, fiber amplifiers, and fiber lasers.     

Gd-based oxyfluoride glass ceramics: Phase transformation,optical spectroscopy and upconverting temperature sensing

A series of precursor glasses with compositions of SiO₂-Al₂O₃-AlF₃-Na₂O- NaF-Gd₂O₃/GdF₃-YbF₃-ErF₃ were prepared and their crystallization behaviors were investigated. For the samples with high F content, meta-stable hexagonal GdF₃ nanocrystals were preferentially precipitated from glass matrix and decreasing F/O ratio induced phase transformation to cubic NaGdF₄ and finally to hexagonal NaGdF₄. Benefited from its multiple active sites, significant enhanced upconversion luminescence was achieved for Yb/Er co-doped glass ceramic containing hexagonal NaGdF₄ nanocrystals. Importantly, significant temperature-sensitive upconversion fluorescence intensity ratio between Er³⁺: ²H_11/2 → ⁴I_15/2 transition (520 nm) and ⁴S_3/2 → ⁴I_15/2 one (540 nm) was detected owing to the competitive radiation transitions from these two thermally coupled emitting-states. Furthermore, linear temperature-dependent fluorescence intensity ratio between Er³⁺: ⁴F_9/2 → ⁴I_15/2 transition (650 nm) to ⁴S_3/2 → ⁴I_15/2 one (540 nm) was achieved, showing the advantages of high sensitivity, superior signal discriminability as well as excellent thermal stability for temperature determination.     

Multicolor upconversion emission and highly optical temperature sensing based on lanthanide-doped double perovskite Sr2LaNbO6 phosphors

Here we adopt trivalent lanthanide (Ln³⁺ = Er³⁺, Er³⁺/Ho³⁺, and Yb³⁺/Tm³⁺) doped Sr₂LaNbO₆ (SLNO) as novel upconversion luminescence (UCL) materials for achieving UCL and optical temperature sensing under 980 nm excitation. Specifically, Er³⁺ single doped Sr₂LaNbO₆ phosphors present bright high-purity green emission under the 980 nm excitation. While co-doping with the Ho³⁺ ions, the component of red emission from Er³⁺ ions increases significantly and sample show a remarkable enhancement of luminescent intensity relative to SLNO:Er³⁺ sample. The above-mentioned phosphors and Yb³⁺/Tm³⁺ co-doped phosphor (blue emission) successfully achieve high-purity trichromatic UCL and mixed white light output in the same host. Furthermore, the temperature sensing performance of the SLNO:Er³⁺/Ho³⁺ phosphor based on the fluorescence intensity ratio (FIR) is systematically studied for the first time. The temperature sensing based on the non-thermal coupling levels (NTCLs) exhibit higher sensitivity than that based on the thermal coupling levels (TCLs). The maximum absolute and relative sensitivity for ⁴F_9/2/⁴I_9/2 NTCLs reach 0.16803 K^?1 at 427 K and 0.01591 K^?1 at 641 K, respectively. Interestingly, NIR emission of ⁴I_9/2 → ⁴I_15/2 transition presents a thermal enhancement, while visible emissions show thermal quenching. These results indicate that the Ln³⁺ doped Sr₂LaNbO₆ UCL phosphors have potential applications in the fields of non-contact temperature sensors, full-color displays, and anti-counterfeiting.     

Spectroscopic analysis of up conversion luminescence in doped halogeno-antimonite glass

The up-conversion emission of Nd³⁺, Sm³⁺ and Er³⁺ has been studied in a new halogeno-antimonite glass with the chemical composition 80 Sb₂O₃ – 10 ZnBr₂ – 10 KCl. Doping concentration was 0.2?mol% of lanthanide (Ln) ions. Rare earths were introduced as fluorides LnF₃ that were further converted into oxides. Main physical properties of base glass were measured, including density, thermal expansion, characteristic temperatures, refractive index and optical transmission. The amount of residual hydroxyls was calculated from the OH absorption band around 3000?nm. The recorded up-conversion emission lines are λ_em =?536?nm for Nd³⁺ pumped at 805?nm; λ_em =?563?nm, 600?nm, 631?nm and 645?nm for Sm³⁺ pumped at 945?nm; λ_em =?531?nm for Er³⁺ pumped at 798?nm. Co-doped glass (0.1 Yb³⁺ + 0.1 Er³⁺) pumped at 980?nm has three emission lines at 524?nm, 545?nm and 650?nm. Corresponding transitions have been identified and the mechanisms ruling the up-conversion process is discussed. They include excited state absorption (ESA), energy transfer (ET) cooperative energy transfer (CET), emission assisted by phonon (EAP), multiphonon relaxation (MR) and cross- relaxation (CR).     

Evolution of Strong Red Upconversion Luminescence in Er3+‐Containing Oxy‐Fluoride Glass and Glass‐Ceramics

The Er³⁺ concentration dependencies of upconversion luminescence in oxy‐fluoride glass and glass‐ceramics containing PbF₂ nanocrystals were investigated. Strong red emission from the ⁴F_9/2 → ⁴I_15/2 transition was observed with the addition of ~0.8 mol% Er³⁺ ions, whereas ~10 mol% of Er³⁺ is required to achieve such emission in several other crystalline hosts. Intensities of red emission further increased with the formation of nanocrystals through heat treatment. The Er³⁺ ions enriched in glass and segregated preferentially inside the PbF₂ nanocrystals that decreased the distance among Er³⁺ ions and thereby facilitated energy transfer.     

Realizing particle population inversion of 2.7 μm emission in heavy Er3+/Pr3+ co-doped low hydroxyl fluorotellurite glass for mid-infrared laser

In this work, the population bottleneck of Er³⁺: ⁴I_11/2 → ⁴I_13/2 was overcome for the first time in heavy Er³⁺/Pr³⁺ co-doped TeO₂–BaF₂–La₂O₃–LaF₃ (TBLL) low hydroxyl fluorotellurite glasses. Infrared emission spectra and fluorescence lifetime decay curves reveal that Pr³⁺ ions could deplete the electrons from the Er³⁺: ⁴I_13/2 level faster than those from the Er³⁺: ⁴I_11/2 under 980 nm excitation. Specifically, the energy transfer (ET) efficiency of the Er³⁺: ⁴I_13/2 → Pr³⁺: ³F_3,4 process (ET1) reached 96.27%, while that of the Er³⁺: ⁴I_11/2 → Pr³⁺: ¹G₄ process (ET2) is only 2.17% in the Er³⁺/Pr³⁺ co-doped glass. Additionally, the energy transfer mechanism of Er³⁺ and Pr³⁺ ions was investigated using the Dexter theory, where the energy transfer microscopic parameters C_D-A are 13.21 × 10⁻⁴⁰ cm⁶/s and 0.89 × 10⁻⁴⁰ cm⁶/s for the ET1 and ET2 processes, respectively. Finally, a numerical simulations laser model was developed to discuss the laser properties of the Er³⁺/Pr³⁺ co-doped TBLL fibers. The simulation results indicate that a 2.7 μm laser with a maximum output power of 2.26 W and slope efficiency of 13.89% could be achieved when the fiber background loss is reduced to 0.5 dB/m. The above results suggest that the Er³⁺/Pr³⁺ co-doped TBLL glass has great potential applications in mid-infrared fiber lasers.     

Intense broadband 3.1 μm emission in Er3+-doped fluoroaluminate-tellurite glass for mid-infrared laser application

Er³⁺ single doped fluoroaluminate-tellurite glasses were made by employing a conventional melt-quenching technique. A strong fluorescence around 3.1 μm was achieved from Er³⁺-doped fluoride glasses, under a 980 nm laser diode pump, which was assigned to the Er³⁺: ⁴S_3/2 → ⁴F_9/2 radiation transition process. The up-conversion and mid-infrared spectra of emission for fluoroaluminate-tellurite glasses with various concentrations of Er³⁺ ions dopant was researched. In addition, the calculated fluorescence lifetime value about 3.1 μm reaches 0.48 ms. The findings indicate that fluoroaluminate-tellurite glasses doped with Er³⁺ have prospects of being developed into 3.1 μm mid-infrared fiber and laser materials.     

Rare‐earth‐doped SiO2‐CaF2 glass ceramic nano‐particle with upconversion properties

Rare‐earth‐doped upconversion nano‐phosphor shows new possibilities in the field of bioimaging because of its unique properties like higher penetration depth, low signal to noise ratio (SNR), good photo stability, and zero auto fluorescence. The oxyfluoride glass system is the combination of both fluoride and oxide where fluoride host offers high optical transparency due to low phonon energy and oxide network offers high physical stability. Thus, in the present work, an attempt has been made to synthesize 1 mol% Er³⁺ doped SiO₂‐CaF₂ glass ceramic nano‐particles through sol‐gel route. The synthesized glass ceramic particles were heat treated at 4 different temperatures starting from 600°C to 900°C.The X‐ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) analysis confirmed the formation of CaF₂ nano‐crystals in the matrix which is 20‐30 nm in size. The vibrational spectroscopic analysis of the glass ceramics sample has been investigated by Fourier transform infrared (FTIR) spectroscopy. The UV‐Visible‐NIR spectroscopy analysis was carried out to analyze the absorption intensity in the near infrared region. Upon 980 nm excitation, the sample shows red emission corresponds to ⁴F_9/2→⁴I_15/2 energy level transition. The prepared nano‐particles showed excellent biocompatibility when tasted on MG‐63 osteoblast cells.     

Improved broadband near-infrared luminescence in Nd3+/Tm3+ co-doping tellurite glass with Ag NPs

The near-infrared (NIR) luminescence in S+E+O bands of tellurite glasses doped with Nd³⁺/Tm³⁺ and Ag nanoparticles (NPs) was investigated. The tellurite glasses were prepared by melt-quenching and heat-treated techniques. Under the excitation of 808 nm laser, Nd³⁺/Tm³⁺ doped tellurite glasses produced three NIR luminescence bands of 1.33, 1.47 and 1.85 μm, originating from Nd³⁺:⁴F_3/2→⁴I_13/2, Tm³⁺:³H₄→³F₄ and Tm³⁺:³F₄→³H₆ transitions respectively. Interestingly, a broadband luminescence spectrum ranging from 1280 to 1550 nm with the FWHM (full width at half maximum) about 201 nm was obtained due to the overlapping of the first two NIR bands. Further, the peak intensity of this broadband luminescence was increased by 75% after the introduction of Ag NPs with diameter in 10–20 nm. The analysis of fluorescence decay shows that compared with the enhanced local electric field, the energy transfer from Ag species to Nd³⁺ and Tm³⁺ ions plays a major role in luminescence enhancement. The findings in this work indicate that tellurite glass co-doped with Nd³⁺/Tm³⁺ and Ag NPs is a potential gain material applied in the S+E+O-band photonic devices.