Tunable quantum dot arrays as efficient sensitizers for enhanced near-infrared electroluminescence of erbium ions

Highly efficient electroluminescence from SnO2 nanocrystals and Er3+ co-doped silica thin film via introducing Ca2

Efficient and stable near-infrared silicon-based light source is a challenge for future optoelectronic integration and interconnection. In this paper, alkaline earth metal Ca2+ doped SiO2-SnO2: Er3+ films were prepared by sol-gel method. The oxygen vacancies introduced by the doped Ca2+ significantly increase the near-infrared luminescence intensity of Er3+ ions. It was found that the doping concentration of Sn precursors not only modulate the crystallinity of SnO2 nanocrystals but also enhance the luminescence performance of Er3+ ions. The stable electroluminescent devices based on SiO2-SnO2: Er3+/Ca2+ films exhibit the power efficiency as high as 1.04×10-2 with the external quantum efficiency exceeding 10%.

Improved Fluorescence and Gain Characteristics of Er-Doped Optical Fiber with PbS Nanomaterials Co-Doping

Er-doped optical fiber (EDF) with ultra-broad gain bandwidth is urgently needed given the rapid advancement of optical communication. However, the weak crystal field of the host silica glass severely restricts the bandwidth of traditional EDF at 1.5 μm. In this study, we theoretically explored the introduction of PbS nanomaterials in the silica network assisted with the non-bridging oxygen. This can significantly increase the crystal field strength of Er³⁺ ions in the local structure, leading to their energy level splitting and expanding the fluorescence bandwidth. Additionally, the PbS/Er co-doped optical fiber (PEDF) with improved fluorescence and gain characteristics was fabricated using modified chemical vapor deposition combined with the atomic layer deposition technique. The presence of PbS nanomaterials in the fiber core region, which had an average size of 4 nm, causes the ⁴I_13/2 energy level of Er³⁺ ions to divide, increasing the fluorescence bandwidth from 32 to 39 nm. Notably, the gain bandwidth of PEDF greater than 20 dB increased by approximately 12 nm compared to that of EDF. The obtained PEDF would play an important role in the optical fiber amplifier and laser applications.

Polycrystalline Er-doped Y3Ga5O12 nanofilms fabricated by atomic layer deposition on silicon at a low temperature and the exploration on electroluminescence performance

Polycrystalline erbium-doped Y₃Ga₅O₁₂ garnet (YGG) nanofilms are deposited by atomic layer deposition on Si substrates after annealing down to 800 °C, based on which ∼1.53 μm electroluminescence (EL) devices are fabricated. The optimal EL performance depends on the adjustment of Y/Ga ratio and Ga₂O₃ interlayer thickness within the nanolaminates, which exert no prominent impact on the crystallization and film morphology of YGG nanofilms. EL spectra reveal that the crystalline structure after annealing impacts the surrounding environment of Er³⁺ ions, leading to different emission peaks. These silicon-based devices present a low turn-on voltage of ∼25 V, while the external quantum efficiency and maximum optical power density reach 2.51% and 10.03 mW cm^-2, respectively. The EL is ascribed to the impact-excitation of doped Er³⁺ ions in polycrystalline YGG nanofilms by energetic electrons, the conduction mechanism of which is confirmed to be the Poole-Frenkel mode. These prototype devices possess excellent stability and can operate for up to 49 hours under continuous current injection, verifying the improvement of device performance by the utilization of gallium in the fabrication of garnet nanofilms. The Si-based YGG:Er EL devices are of promising potential for integrated optoelectronic applications.

Efficient Sensitized Photoluminescence from Erbium Chloride Silicate via Interparticle Energy Transfer

In this study, we prepare Erbium compound nanocrystals and Si nanocrystal (Si NC) co-embedded silica film by the sol-gel method. Dual phases of Si and Er chloride silicate (ECS) nanocrystals were coprecipitated within amorphous silica. Effective sensitized emission of Er chloride silicate nanocrystals was realized via interparticle energy transfer between silicon nanocrystal and Er chloride silicate nanocrystals. The influence of density and the distribution of sensitizers and Er compounds on interparticle energy transfer efficiency was discussed. The interparticle energy transfer between the semiconductor and erbium compound nanocrystals offers some important insights into the realization of efficient light emission for silicon-based integrated photonics.

Multiple channels to enhance near-infrared emission from SiO2-SnO2:Er3+ films by Ba2+ ion doping

Ba²⁺ ions co-doped SiO₂-SnO₂:Er³⁺ thin films are prepared using a sol-gel method combined with a spin-coating technique and post-annealing treatment. The influence of Ba²⁺ ion doping on the photoluminescence properties of thin films is carefully investigated. The enhancement of near-infrared (NIR) emission of Er³⁺ ions by as much as 12 times is obtained via co-doping with Ba²⁺ ions. To illustrate the relevant mechanisms, X-ray diffraction, X-ray photoelectron spectroscopy and comprehensive spectroscopic measurements are carried out. The enhanced NIR emission induced by Ba²⁺ co-doping can be explained by more oxygen vacancies, improved crystallinity and strong cross-relaxation processes between Er³⁺ ions. The incorporation of Ba²⁺ ions into SiO₂-SnO₂:Er³⁺ thin films results in a considerable enhancement in the NIR emission, making the thin films more suitable for Si-based optical lasers and amplifiers.

Confinement effect and low-defect density-induced long lifetime Er silicate nanowire embedded in silicon oxide film

In this study, we have developed a reduced Er-Er interaction strategy for pursuing long lifetime and high efficiency luminescence in Er compounds with higher Er concentration. Annealing temperature and atmosphere dependence of the optical properties from Er silicate nanowires embedded in silicon oxide films have been investigated. The record long lifetime α-Er₂Si₂O₇ of 844 µs is achieved through simultaneously reducing defect density and Er-Er interaction. The low-defect density in the α-Er₂Si₂O₇ nanowires is mainly attributed to following aspects: no hydroxyl groups contamination, effective surface passivation and saturation of oxygen vacancies. The interaction of Er-Er ions is confined by the alteration of phonon density of states effects in the α-Er₂Si₂O₇ nanowires. More significantly, the up-conversion emissions in the α-Er₂Si₂O₇ nanowires also reduce effectively because of the nanoconfinement effect.

Plasmon-enhanced upconversion luminescence in pyrochlore phase Yb x Er2-x Ti2O7 thin film

Pyrochlore phase Yb _x Er_2-x Ti₂O₇ (YETO) thin films have been prepared by employing a facile sol-gel method combining with spin-coating technique and post-annealing treatment at 700 °C. High concentration of Yb³⁺ ions can promote the transformation from Yb³⁺/Er³⁺ co-doped anatase phase TiO₂ to pyrochlore phase YETO at 700 °C temperature. We find that the YETO thin film with 30 mol% Yb³⁺ ions exhibits the brightest upconversion (UC) emission. Moreover, the introduction of Au nanorods (Au NRs) in the YETO thin film can further enhance the UC fluorescence. By adjusting the density of Au NRs, the UC emission intensity is increased by about 2.8-fold due to the excitation field enhancement caused by the localized surface plasmon resonance effect.

Investigation of energy transfer mechanisms in rare-earth doped amorphous silica films embedded with tin oxide nanocrystals

Three different types of rare earth (RE³⁺) ions-doped silica thin films are fabricated by a soft chemistry-based method. By introducing tin oxide (SnO₂) nanocrystals with larger cross-sections as sensitizers, the characteristic emission intensity of RE³⁺ ions in amorphous silica thin films can be enhanced by more than two orders of magnitude via the energy transfer process. The possible energy transfer processes under different local environment are revealed by using Eu³⁺ ions as an optical probe. Quantitative studies of PL decay lifetime and temperature-dependence PL spectra suggest that the partial incorporation of RE³⁺ ions into SnO₂ sites gives rises to the change of crystal-field symmetry and the significant enhancement of energy transfer efficiency. Further, typical analytical energy dispersive X-ray spectroscopy (EDS) mapping results prove that part of Eu³⁺ ions doped into the SnO₂ sites after annealing at 1000 °C. We anticipate that our results would shed light on the future research on the energy transfer mechanisms under different local structures of RE³⁺ ions.

Strain-Controlled Recombination in InGaN/GaN Multiple Quantum Wells on Silicon Substrates

This paper reports the photoluminescence (PL) properties of InGaN/GaN multiple quantum well (MQW) light-emitting diodes grown on silicon substrates which were designed with different tensile stress controlling architecture like periodic Si δ-doping to the n-type GaN layer or inserting InGaN/AlGaN layer for investigating the strain-controlled recombination mechanism in the system. PL results turned out that tensile stress released samples had better PL performances as their external quantum efficiencies increased to 17%, 7 times larger than the one of regular sample. Detail analysis confirmed they had smaller nonradiative recombination rates ((2.5~2.8)×10^-2 s^-1 compared to (3.6~4.7)× 10^-2 s^-1), which was associated with the better crystalline quality and absence of dislocations or cracks. Furthermore, their radiative recombination rates were found more stable and were much higher ((5.7~5.8) ×10^-3 s^-1 compared to [9~7] ×10^-4 s^-1) at room temperature. This was ascribed to the suppression of shallow localized states on MQW interfaces, leaving the deep radiative localization centers inside InGaN layers dominating the radiative recombination.