“In the field of high-power lighting phosphors, researchers have made new progress. They have explored the underlying mechanism of negative thermal quenching (NTQ) in Eu2+-doped Na3Sc2(PO4)3 ionic conductors, which provides a new direction for understanding the NTQ mechanism of luminescence via dynamic defects/ions.”
WANG Shijie,WANG Yinghan,TAO Zhengren,AN Zhengce,YE Shi
摘要:Eu2+-doped Na3Sc2(PO4)3 ionic conductor possesses superior thermal quenching(TQ)resistance, which is considered as a promising phosphor for high-power lighting applications. Yet the underlying mechanism of negative thermal quenching(NTQ) is not fully understood. In this study, we focus on upconversion(UC) and downshifting(DS) luminescence of Yb3+/Er3+ with f-f transition rather than susceptible d-f transition of Eu2+ in Na3Sc2(PO4)3, aiming to get a more insightful view. The results show that thermally accelerated dynamic defects/ions contributes to the significant negative thermal quenching(NTQ) of UC luminescence and thermally stabilized DS luminescence by promoting the radiative transition and suppressing the non-radiative transition. The UC process with slow population rate is more susceptible to perturbation of Na+ migration process with time scale equivalent to that of the former, resulting in evident NTQ of UC luminescence. This research opens an avenue for understanding the NTQ mechanism of luminescence via dynamic defects/ions.
关键词:Na3Sc2(PO4)3∶Yb3+,Er3+;upconversion luminescence;Downshifting Luminescence;Negative thermal quenching;energy transfer
摘要:Perovskite materials, with their adjustable bandgaps, high light absorption coefficients, and low exciton binding energies, have shone brightly in the fields of semiconductor photovoltaics and photoelectric detection. The absorption range of universal lead-based perovskites is usually concentrated in the UV to Vis region, while the absorption spectra of narrow-bandgap pure tin-based or tin-lead mixed perovskites are still limited to the NIR range within ~1 060 nm, constrained by the application and detection imaging in future complex scenarios. Combining perovskites with narrow-bandgap semiconductors to construct “perovskite/semiconductor” composite heterostructures can further expand the spectral range and enhance absorption efficiency. This review summarizes the progress in optimizing detection performance, the exceptional properties of monomaterials, and the preferred engineering of composite materials for perovskite-based broadband photodetectors. It also discusses the advancements and application prospects of broadband detectors in terms of spectral response, pixel integration, development of flexible devices, and stability. This review aims to promote research in perovskite-based wide-band photodetection and its future imaging applications.
摘要:The SiC substrate is a good candidate for preparing high-performance AlGaN-based deep ultraviolet (DUV) lasers. The DUV AlGaN/AlN multiple quantum wells (MQWs) structures were grown on 4H-SiC substrates by metal-organic chemical vapor deposition (MOCVD). The effects of MQWs growth parameters on the spontaneous and stimulated emission characteristics of the DUV laser structure were systematically studied. After the comprehensive analysis of the surface morphology and emission properties of MQWs, it was found that with the increase in NH3 flow rate and growth temperature, the surface roughness of MQWs decreased and the internal quantum efficiency increased to 74.1%. At room temperature, the lasing wavelength, threshold optical power density and linewidth were 248.8 nm, 1.03 MW/cm2 and 1.82 nm, respectively. The high NH3 flow rate and growth temperature suppress the incorporation of carbon impurities in the active region, leading to an increase in carrier radiative recombination efficiency and material gain. Simultaneously, the reduced growth rate improves the surface morphology of the MQWs structure and reduces interfacial scattering losses. Furthermore, smooth and steep facets were prepared by combining dry etching and wet etching processes, which reduced the mirror loss of the laser. The threshold optical power density and linewidth were decreased to 889 kW/cm2 and 1.39 nm, respectively.
关键词:Aluminum gallium nitride;Silicon carbide;Optically pumped laser;Ⅴ/Ⅲ ratio;growth temperature
摘要:Crystals of Er3+/Yb3+/Pr3+∶SrLaGaO4, Er3+/Yb3+∶SrLaGaO4, and Er3+∶SrLaGaO4 were successfully grown using the non-stoichiometric ratio Czochralski method, and detailed spectroscopic analyses were conducted. Additionally, thermal performance analyses were performed on pure SrLaGaO4 crystals. Compared with Er3+∶SrLaGaO4 crystal, Er3+/Yb3+/Pr3+∶SrLaGaO4 crystal not only shows better absorption characteristics but also exhibits weaker near-infrared emissions, as well as superior mid-infrared emissions. Furthermore, the self-termination effect for the 2.7 μm erbium laser is suppressed successfully since the fluorescence lifetime of the 4I13/2 lower level of Er3+ decreases markedly while that of the upper 4I11/2 level falls slightly in Er3+/Yb3+/Pr3+∶SrLaGaO4 crystal. Besides, the sensitization effect of Yb3+ ion and deactivation effect of Pr3+ ion as well as the energy transfer mechanism in Er3+/Yb3+/Pr3+∶SrLaGaO4 crystal were studied in this work. In conclusion, the introduction of Yb3+ and Pr3+ ions is favorable for achieving an enhanced 2.7 μm emission in Er3+/Yb3+/Pr3+∶SrLaGaO4 crystal which can act as a promising candidate for mid-infrared lasers.
摘要:Red phosphor is an important component to improve the color rendering index and reduce the color temperature of white light emitting diode (LED). In this paper, we select Eu3+ with characteristic red emission as activator ions, and new phosphate Sr2InP3O11 is used as the phosphor host. A series of Sr2-xInP3O11∶xEu3+ (simplified as S2-xIP3∶xEu3+) and Sr2In1-xP3O11∶xEu3+ (simplified as S2I1-xP3∶xEu3+) phosphors were synthesized through high temperature solid state reaction. The photoluminescence performance and the effect rule of cation sites (Sr sites and In sites) of phosphor were detailly studied by XRD, room and variable temperature PL spectra, quantum efficiency and fluorescence lifetime. The results show that these two types of phosphors can emit bright red light (dominating by 593 nm and 612 nm) under the radiation of 254 nm and 393 nm. In addition, these synthesized phosphors have average color stability and thermal stability, which indicates that they have certain development potential in the field of phosphor conversion white LED lighting and displaying.
摘要:The ZnGa2O4∶xCr3+,yMgF2 phosphors were synthesized using the high-temperature solid-state reaction method, and their phase structure and luminescence properties were investigated. The results show that F ions play a crucial role in MgF2 doping, which substitute for O anions to form multiple Cr3+ centers of [CrO6] and [Cr(O,F)6] with different local environments, thereby significantly broadening the emission spectra of ZnGa2O4∶Cr3+. Furthermore, tunable emission bands peaking from 689 nm to 900 nm are achieved by increasing the Cr3+ concentration. Steady-state and transient-state spectroscopic analysis shows that the energy transfer between multiple Cr3+ centers accounts for the significant red-shift of emission bands with increasing the Cr3+ concentration. The optimized sample ZnGa2O4∶0.1Cr3+,0.2MgF2 (ZMGOF∶0.1Cr3+) exhibits a broadband near-infrared (NIR) emission ranging from 700 nm to 1 200 nm under the blue light excitation, with a maximum emission wavelength of 885 nm and a full width at half maximum (FWHM) of 215 nm. Meanwhile, the ZMGOF∶0.1Cr3+ phosphor shows high luminescent efficiency and good thermal stability, for which an internal (external) quantum efficiency of 92.3% (48.1%) is achieved and 89.6% of the initial intensity can be maintained at 100 ℃. By combining the ZMGOF∶0.1Cr3+ phosphor with the blue chip, a pc-LED device was fabricated with a NIR output power of 34.5 mW and an energy conversion efficiency of 12.3% at 100 mA driving current.
摘要:Near-infrared phosphor-converted light-emitting diodes (pc-LEDs) are characterized by their compact size and high efficiency, making them a promising solution for various applications in non-destructive testing and biological imaging. In this paper, we successfully synthesized Ca3Nb1.6875Ga3.1875O12∶Cr3+ phosphor through the high-temperature solid-state method. This phosphor displays broadband near-infrared emission ranging from 650 nm to 1 000 nm, with a peak wavelength of 770 nm when excited by 460 nm blue light. The crystal structure and spectral data of the material were systematically analyzed, and parameters such as the crystal field strength of Cr3+ in CNGG matrix were calculated. The thermal stability of phosphorescence was significantly improved by introducing Zn2+, and the possible reasons were analyzed. The combination of CNGG∶Cr3+ with a blue light chip was encapsulated into a near-infrared pc-LED, leading to its successful application in the realm of biological tissue imaging.
摘要:The up-conversion luminescent material KYb2F7∶2% Er3+ was synthesized using the hydrothermal method. The synthesized sample was confirmed to be pure phase with an orthorhombic morphology by X-ray diffraction and scanning electron microscopy. Under 980 nm laser excitation, the sample exhibited two green emission peaks at 527 nm and 543 nm, as well as a dominant red emission peak at 655 nm. The temperature-dependent upconversion (UC) emission spectra showed that the emission intensity at 545 nm and 655 nm exhibited thermal quenching with increasing temperature. Based on the mechanism of thermal coupling temperature measurement, the temperature sensing performance of 2H11/2→4I11/2 and 4S3/2→4I11/2 thermal coupling energy levels of Er3+ was studied, and the luminous intensity ratio (LIR), absolute sensitivity (Sa), relative sensitivity (Sr), temperature uncertainty (δT), and repeatability (R) of the luminous thermometer were calculated. The maximum relative sensitivity was 0.99%·K-1 at 313 K, the minimum temperature uncertainty was 0.73 K at 313 K, and the repeatability exceeded 99%, ensuring the reliability of the thermometer. All the experimental results indicate that KYb2F7∶2% Er3+ has potential application value in temperature sensing.
摘要:Na3Y(VO4)2∶Yb3+/Er3+ upconversion (UC) material is synthesized by the high-temperature solid-state method, exhibiting strong luminescence in both green and NIR-Ⅱ region. In green region, optical thermometry based on the fluorescence intensity ratio (FIR) of Er3+:2H11/2→4I15/2 and 4S3/2→4I15/2 transition achieves optimal absolute sensitivity (SA), relative sensitivity (SR) and temperature resolution (δT) of 1.7%·K-1, 1.2%·K-1 and 0.027 K, respectively. In NIR-Ⅱ region, optical thermometry based on the Stark splitting of Er3+:4I13/2→4I15/2 transition exhibits optimal SA, SR and δT of 3.01%·K-1, 0.59%·K-1 and 0.06 K, respectively. More importantly, both of the two optical thermometers show high accuracy for temperature measurement within the physiological temperature range. All data indicate that Na3Y(VO4)2∶Yb3+/Er3+ is an excellent luminescence material with the ability of high-sensitivity dual-mode optical thermometry in the visible and NIR region.
关键词:rare earth ions;upconversion luminescence;optical thermometry;fluorescence intensity ratio
摘要:A novel Ca5-xGa6O14∶xSm3+ mechanoluminescent (ML) material was successfully prepared by high-temperature solid-state reaction method. The crystal structure, surface morphology, photoluminescence, ML properties and luminescence mechanism of Ca5-xGa6O14∶xSm3+ were investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflection spectra, photoluminescence excitation and emission spectra, luminescence decay, ML spectra and thermoluminescence spectra. Under the excitation of 404 nm, the emission peaks at 562, 599, 642, 715 nm are detected in Ca5-xGa6O14∶xSm3+, corresponding to 4G5/2→6Hj(j=5/2, 7/2, 9/2, 11/2) characteristic emission of Sm3+. With the increase of Sm3+ content, the luminescence intensity first increases and then decreases, the optimal luminescence intensity is obtained at x=0.07 and the decay time decreases from 1.92 ms to 1.30 ms. Under the sliding friction, ML emission band is obtained in Ca5-xGa6O14∶xSm3+, and the ML intensity increases linearly with applied stress, indicating that the material has potential application in the field of stress sensors.
摘要:In this study, we designed a new parameter, the temperature impact factor, which considers the spacing between vertical-cavity surface-emitting laser (VCSEL) array units, size of the oxidation aperture, number of units, and the input current, and can be used to characterize the degree of thermal crosstalk in the array. Based on this, we designed an optimization layout algorithm for the VCSEL array and established a thermal-electric coupling model to verify the benefits of the optimized layout on temperature characteristics. Compared with the conventional layout, the temperature rise was reduced by 5%. In addition, under the condition of fixed current density and luminous area, reduction of the oxidation aperture and increasing the number of units can effectively improve the temperature characteristics of the VCSEL array. The average temperature of the 10 μm oxidation aperture was 30 K lower than that of the 30 μm oxidation aperture. The research results show that the impact of thermal crosstalk in the VCSEL array is effectively reduced and provide guidance for the design of the VCSEL array.
摘要:The integration of light source and detector can effectively promote the development of lightweight and miniaturized photoelectricity systems. The coexistence of emission and detection in InGaN/GaN multi-quantum well (MQW) light emitting diode devices provides a possibility for the design of transceiver integrated devices. In this paper, InGaN/GaN MQW microdisk array integrated on silicon wafers were fabricated using standard semiconductor processes, and their emission, detection, and basic communication characteristics were studied. The resonance mode in the microdisk device helps to improve its detection characteristics, while the isotropic radiation characteristics help the device as a light source and the detector in space coupling. As a light source, the device operates at 2.5 V with an emission wavelength at 455 nm and a -3 dB bandwidth reaching 5.4 MHz. As a detector, the device is responsive to light in the ultraviolet to blue band, and the detection performance decreases with increasing wavelength with a cutoff wavelength of 450 nm. Under excitation at 365 nm, the device exhibits a switch ratio of 7.2×104 with a fall time as short as 0.41 ms. Additionally, we constructed and demonstrated a half-duplex communication system based on a single device that achieved data transmission in different frequency bands. This research is of great significance for the preparation of electrically driven light source and the optical communication of transceiver integration.
关键词:silicon-based InGaN/GaN;multiple quantum well devices;luminescence and detection;half-duplex communication
摘要:Novel near-infrared organic photodetectors have wide application prospects in biosensing, medical imaging, and wearable electronics with the advantages of low cost, solution-spin coating, good biocompatibility, and flexible. Compared with diode organic photodetectors, high sensitive photomultiplication organic photodetectors have attracted enormous attention because of their higher external quantum efficiency (EQE>100%). The mechanism of the photomultiplication involves a type of carrier being trapped near the electrode, which assists another opposite polarity carrier tunneling into the active layer from the extra circuit. However, the performances of the device are limited by the number of traps. In this work, inorganic ZnO nanoparticles (NPs) are added into the active layer to enhance the photocurrent of the device through increasing the number of electron traps, and fortunately the dark current density of the device is maintained. It is found that the photocurrent of the device is improved by 7.4 times with optimal 5% ZnO NPs, compared with control device without ZnO NPs, under the reverse bias of -15 V, 850 nm illumination. Besides, the Al2O3 interface modification layer is further inserted into the device to improve performance of the device. The results show that the Al2O3 based device has bi-direction response for both reverse and forward bias via changing the interface contact characteristics near anode. Ultimately, the device obtains high EQE and R up to 105% and 104 A/W at a broad wavelength range of 380-1 310 nm, applied with a forward bias of 15 V. This work provides a new idea and method for the development of high-sensitivity organic photodetectors.
摘要:Interface engineering at the bottom can effectively enhance the efficiency and stability of perovskite solar cells. In this study, the surface modifier, bis (triphenylphosphine) cobalt chloride (BTPPCC), was employed as a pre-buried interface modifier, successfully passivating the surface-enriched defects of MAPbI3 perovskite films. This optimization improved the interface contact between the perovskite film and the underlying hole transport layer (HTL), enhancing the crystalline performance of the perovskite absorption layer. Additionally, BTPPCC effectively suppressed non-radiative recombination at the interface, improving the long-term stability of the device. As a result, the power conversion efficiency (PCE) of the p-i-n type device increased from 18.37% to 20.12%. The unencapsulated device maintained an efficiency of over 76% after continuous operation for nearly 500 hours in an ambient air environment with a relative humidity (RH) of 50% at room temperature. This study provides an effective method for optimizing the buried interface in perovskite solar cells.
关键词:perovskite solar cells;buried bottom interface;defect passivatio
摘要:White organic light-emitting diodes (WOLEDs) are widely used in display and lighting applications due to the advantages of surface light source, flexibility, thinness, and self-emission. Highly efficient solution-processed hybrid white light-emitting organic light-emitting diodes (WOLEDs) are seldom reported. In this paper, we chose the blue thermally delayed fluorescent material DMAC-DPS to be the sensitised host of the conventional orange phosphorescent material PO-01-TB, and prepared thermally activated sensitised hybrid single light-emitting layer organic light-emitting diode white-light devices, and analysed the mechanism of the energy transfer of the devices. The highest external quantum efficiency of 8.00%, current efficiency of 22.32 cd/A, corresponding to the CIE coordinates (0.405, 0.497) and a warm white OLED device with a color temperature of 4 059 K were achieved through the modulation of the doping concentration of the host and the guest. The addition of a hole-blocking layer, DPEPO, effectively improves the spectral stability of the device and achieves a smaller ΔCIE (0.017, 0.016). This study inspires the development of efficient WOLEDs in the future.
关键词:white organic light-emitting diodes;thermally activated delayed fluorescence materials;solution treatment;energy transfer
摘要:Circulating tumor cells (CTCs) are cells that are shed from the primary or metastatic site of a malignant tumor and circulate through the bloodstream to reach the body. Therefore, the presence of CTCs in vivo can reflect the occurrence and development of tumors, which is crucial for the diagnosis and prognosis of tumors. However, there are still many challenges to achieving high purity capture and post-capture CTCs inactivation blocking. Among the schemes developed for selective separation of CTCs, fluorescence method has an important application prospect in non-invasive detection and rapid detection because of its high sensitivity, high resolution and simple operation. Compared with previous CTCs research reviews, this paper describes the whole process of CTCs from in vitro capture to in vivo capture to downstream analysis in detail, and systematically and detailedly summarizes the complete diagnosis and treatment process of CTCs, providing new ideas for current research. This is of great significance for the diagnosis and treatment of early circulating tumor cells.
摘要:In recent years, it has been observed that several radiophotoluminescent materials used for radiation detection have been widely used in the fields of dose monitoring in nuclear decommissioning facilities, fluorescent nuclear trace detection, medical therapy, radiation imaging and visualisation of nuclear radiation sites due to their high measurable dose limits and wide dose ranges. This study provides an overview of the current research state of radiophotoluminescent materials suitable for high-dose measurements, including inorganic activator ion doping systems, inorganic undoped systems, and organic polymer systems. The focus is on reviewing the luminescence mechanism, basic characteristics, types, and application status of each system. At the same time, a comparative analysis is conducted to examine the influence factors of the response to radiation doses and the performance advantages and disadvantages in different system materials. This study aims to provide a summary of the current research on the enhancement of dose detection performance of radiophotoluminescent materials suitable for high-dose measurements. Concurrently, the feasibility measures for improvement and optimization are put forward, and the future development trend is forecasted.