“In the realm of OLED technology, a new method has been developed to enhance efficiency and color purity while reducing costs. Researchers have utilized a platinum complex as a sensitizer and MR-TADF molecules as emitters, achieving a maximum EQE of 13.6% with minimal efficiency roll-off. This innovation paves the way for more affordable, high-performance OLEDs.”
摘要:Although organic light-emitting diodes (OLEDs) have been commercialized and become popular in smartphone, the vacuum deposition process makes them too expensive for mass production and less cost-effective. Herein, we employed highly emissive platinum complex as the sensitizer and multi-resonant thermally activated delayed fluorescence (MR-TADF) molecules as the emitters to demonstrate highly efficient, high color purity, and solution-processed OLEDs with the alleviated efficiency roll-offs. The triplet excitons are rapidly converted to singlet excitons assisted by the phosphorescent sensitizer. Attributed to the reduced triplet exciton lifetime induced by the phosphorescent sensitizer, the MR-TADF OLEDs exhibited a maximum external quantum efficiency (EQE) of 13.2% with a low efficiency roll-off of 25.8% at 1 000 cd/m². To reduce Dexter energy transfer between phosphorescence sensitizer and the emitter, an analogue TADF emitter with the peripheral bulky blocking units was employed, which rendered an improved maximum EQE of 13.6%. This investigation presents a general approach to realize high-performance solution-processed electroluminescence.
摘要:Single-crystal semiconductors such as silicon, germanium, and gallium arsenide consistently demonstrate higher photovoltaic conversion efficiencies in the field of solar energy. However, in the third-generation thin-film solar devices based on ABX3 type novel organic-inorganic hybrid metal halide perovskite materials, the latest certified efficiency of over 26% has been achieved using polycrystalline thin films, while the highest efficiency for single-crystal perovskite solar cells is approximately 24%, with limited related research. Polycrystalline perovskite thin films exhibit high-density intrinsic structural defects (grain boundaries, vacancy defects, impurity defects, antisite defects, etc.), leading to issues of poor device stability and hysteresis effects, among others. In contrast, single-crystal perovskites offer advantages such as absence of grain boundaries, low defect density, long carrier lifetime, and long diffusion lengths. These characteristics position single-crystal perovskites as ideal candidates for high-performance optoelectronic devices. In the trajectory of semiconductor photovoltaic materials, the single-crystals remain the ultimate commercialization target. This review briefly outlines the basic device structure of single-crystal perovskite solar cells, systematically evaluates the advantages and disadvantages of various constituent single-crystal perovskite materials, explores diverse single-crystal perovskite material preparation/growth methods, and critically analyzes the latest research advancements, with an emphasis on the interplay among single-crystal perovskite material composition, device structure, preparation methods, and performance. It is hoped that this review will provide valuable insights to catalyze the development of highly efficient and stable single-crystal perovskite solar cells by researchers in the field.
关键词:perovskite solar cells;single-crystal perovskite;defects;space-limited inverse temperature crystallization
摘要:Mid-infrared fiber lasers operating at 3 μm bands have attracted considerable attention due to their potential applications in medicine, environmental monitoring, military defense, etc. One of the key foundations to achieve 3 μm mid-infrared fiber laser is the gain medium made by efficient and stable glass host materials with low phonon energy. In this study, novel Er3+-doped Al2O3-CaO-ZnO glasses were synthesized by melt-quenching method. Properties of thermodynamic, structure, transmission wavelength range, and mid-infrared emission were studied by thermal analysis, Raman spectra, transmission spectra, and photoluminescence spectra. The results showed that Al2O3-CaO-ZnO glasses possess a high glass transition temperature (~750 ℃), low phonon energy (~780 cm-1), and wide transmission wavelength range (0.5-5 μm). Besides, intense 2.7 μm emissions originating from Er3+: 4I11/2→4I13/2 transition were observed in glass under 980 nm laser diode excitation. Our results indicate that Al2O3-CaO-ZnO glasses could be a potential host material for mid-infrared laser.
摘要:Near-infrared phosphors have garnered significant research attention due to their unique physical properties and broad application prospects. In this work, we synthesize the Sr9Ga(PO4)7∶0.8Cr3+ near-infrared phosphors through high-temperature solid phase reaction. The Sr9Ga(PO4)7∶0.8Cr3+ emitted light at a wavelength of 833 nm with a full width at half maximum of 117 nm excited by blue light at 460 nm. Rare-earth ions were also incorporated into the Sr9Ga(PO4)7∶0.8Cr3+,Yb3+ and Sr9Ga(PO4)7∶0.8Cr3+,Nd3+. The Sr9Ga(PO4)7∶0.8Cr3+ was compared with Sr9Ga(PO4)7∶0.8Cr3+,Yb3+ which emits characteristic peaks of Cr3+ and Yb3+ when excited by 460 nm blue light. Spectroscopic analysis and decay curves changes confirm the existence of a Cr3+-Yb3+ energy transfer channel with a maximum energy transfer efficiency of 80.2%. The thermal stability of Sr9Ga(PO4)7∶0.8Cr3+,Yb3+ has improved the overall fluorescence spectrum by about 3.7 times due to the excellent thermal stability of Yb3+. Sr9Ga(PO4)7∶0.8Cr3+,Nd3+ samples were designed and synthesized to show the multi-peak emission at 833, 876, 1 060 nm. Finally, we discuss the potential applications of these phosphors in temperature sensing and non-destructive testing, demonstrating their exciting application prospects.
摘要:A series of NaYSiO4∶xCe3+ (0.01≤x≤0.05) blue phosphors were synthesized by high-temperature solid-state reaction method. NaYSiO4∶xCe3+ phosphors have a broadband absorption in the 250-360 nm region, which can be well matched with ultraviolet (UV) LED chips. There exist multiple Ce3+ luminescence centers in the NaYSiO4∶xCe3+ phosphors, which exhibits a broadband blue emission with peak wavelength near 414 nm under UV excitation. Measured across the UV region (300-350 nm), the quantum efficiencies of NaYSiO4∶0.02Ce3+ phosphor can remain larger than 25%. The NaYSiO4∶0.02Ce3+ phosphor shows excellent chemical stability, and its emission intensity and quantum efficiency were almost unchanged after being soaked in water for 14 days. The observed significantly spectral blue-shift and rapidly reduced half-maximum full width (FWHM) in the temperature-dependent emission spectra of the NaYSiO4∶0.02Ce3+ sample can be attributed to the thermally activated phonon-assisted tunneling effect. A bright white light emitting diodes (WLED) with a color rendering index of 95 can be fabricated by depositing the NaYSiO4∶0.02Ce3+ blue phosphor, commercial (Sr,Ba)2SiO4∶Eu2+ green phosphor and commercial (Ca,Sr)AlSiN3∶Eu2+ red phosphor on 310 nm UV LED chip. When the drive current gradually increases from 50 mA to 300 mA, the fabricated LED device shows a stable warm-white light emission with almost unchanged color coordinates. These results indicate that NaYSiO4∶0.02Ce3+ blue phosphor reported here has a potential application in UV LED chip pumped WLED lighting.
关键词:NaYSiO4∶Ce3+;high-temperature solid-state reaction method;blue phosphor;white light emitting diodes;high color rendering index
摘要:White LED as the fourth generation of lighting light source has been widely used in various areas of people’s life, in which phosphor is one of the key materials to obtain high performance white LED. How to prepare high-performance phosphors in a simple way is a challenging task for researchers nowadays. In this paper, BaAl4Sb2O12∶Eu2+(BASO∶Eu2+) phosphors were successfully prepared by using a high-temperature solid-phase method with the addition of fluxes H3BO3, NH4Cl, SrF2, LiF and BaF2. The crystal structure analysis, emission spectra, X-ray photoelectron spectroscopy (XPS), and fluorescence lifetime showed that the excess Sb2O3 could effectively reduce Eu3+ to Eu2+, increase the fluorescence intensity of Eu2+ at 563 nm by about 12.5 times, and the internal quantum efficiency (IQE) could reach 96.14 %. And the effects of different fluxes on the crystal structure, fluorescence intensity and internal quantum efficiency of phosphor were investigated. The method adopted in this experiment is simple, avoids the use of hazardous reducing gas sintering, and is easy to be applied industrially and reduce the production cost.
摘要:Transition-metal Mn2+ ion doped garnet phosphor ceramics are promising for laser lighting with high color rendering. However, the scheme for Mn2+ doped garnet ceramics is still ambiguous due to the diversity of ionic radii of Mn2+ in different coordinate environment. In this study, two series of YAG∶Ce3+ phosphor ceramics with different Mn2+ concentrations occupying octahedral(OC) and dodecahedral(DO) lattice sites were fabricated by vacuum sintering. The crystal structure, photoluminescence, fluorescence decay curves, quantum efficiency and electro-luminescence properties were studied in detail. The garnet crystal structure with Mn2+ occupying in octahedral (OC) sites was more stable under the premise of doping SiO2 as charge and volume compensator. Therefore, the quantum efficiency of the OC series samples was higher than that of the DO series, in case the Mn2+ concentration fixed at 0.5%-6%(at). In addition, emission bands of OC series samples peaked at 588 nm and 725 nm, were corresponding to the 4T1→6A1 transitions of Mn2+ located at octahedral, and dodecahedral sites, respectively. The emission peak at 572 nm in the DO series was assigned to the transition of Mn2+ occupying in distorted dodecahedral sites. Benefiting from the efficient energy transfer from Ce3+ to Mn2+, the CRI and CCT of 70.8 and 5 117 K, respectively, were acquired from the white LD lighting device structured by YAG∶Ce3+ phosphor ceramics with 6%(at) Mn2+ occupying in octahedral site. This study presents a strong supplement to the research on Mn-doped garnet luminescent materials, and provides a reference for improving the color rendering performance of laser lighting sources by adding the red spectral component of YAG∶Ce3+ phosphor ceramics, further driving their application in the field of medical treatment and display.
摘要:The Dy2Zr2O7 powder with an average particle size of ~150 nm was prepared by a solid-state reaction method from the chemically precipitated Dy2O3 particle and the commercial ZrO2 powder. After cold isostatically pressing and vacuum sintering, the magneto-optical transparent Dy2Zr2O7 ceramic was successfully fabricated. The obtained Dy2Zr2O7 ceramic material has the typical defective fluorite structure feature with an in-line transmittance of ~68% at 635 nm (~88% of the theoretical transmittance). The developed magneto-optical transparent Dy2Zr2O7 ceramic has Verdet constants of (-182±7), (-118±2), (-48±1) rad·T-1·m-1 at 635 nm, 780 nm and 1 064 nm, respectively, which are roughly 1.33- and 1.24-fold higher than the commercial terbium gallium garnet crystal at 635 nm and 1 064 nm, respectively. The results show that the Dy2Zr2O7 transparent ceramic is a potential new magneto-optical material.
“Indium phosphide (InP), a significant III-V semiconductor material, has been extensively studied for its unique optical and electrical properties, with potential applications in optoelectronics, catalysis, and medicine. Researchers have successfully synthesized high-quality InP nanowires and nanopillars using chemical vapor deposition (CVD) and in-situ growth methods, respectively. The nanomaterials were characterized using SEM, EDS, XPS, Raman spectroscopy, and TEM, revealing a high degree of crystallinity and single crystal structure. The growth mechanisms were identified as vapor-liquid-solid (VLS) for nanowires and solid-liquid-solid (SLS) for nanopillars, offering new insights into the controlled preparation and large-scale production of InP nanomaterials.”
摘要:Indium phosphide (InP) is an important Ⅲ⁃Ⅴ semiconductor material that has recently received considerable attention because of its unique optical and electrical properties. Numerous studies have demonstrated its potential applications in optoelectronics, catalysis, and medicine. However, challenges remain in the controllable preparation and large-scale synthesis of low dimensional InP nanomaterials. In addressing these issues, we successfully produced a remarkable quantity of high-quality InP nanowires on Si/SiO2 substrates using chemical vapor deposition (CVD). In addition, we grew a substantial amount of InP nanopillars on polycrystalline InP substrates using the in-situ growth method. The nanomaterials were observed using scanning electron microscopy (SEM). The nanowires had smooth surfaces with diameters ranging from 30 nm to 65 nm, and the film composed of nanowires was approximately 35 μm thick. The nanopillars had diameters distributed in the range of 550-850 nm, and the film composed of nanopillars was approximately 12 μm thick. The nanomaterials were analyzed using energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) to determine their composition, which was found to be InP. Raman spectroscopy was used to determine the chemical structure of the nanomaterials, which was further analyzed. Transmission electron microscopy (TEM) was used to observe the microstructure of the nanomaterials. The nanowires prepared for this study were found to have a high degree of crystallinity, with growth in the [111] direction. Analysis of the nanowire crystal properties using selected area electron diffraction (SAED) revealed clear diffraction points indicating a single crystal structure. Luminescence properties were analyzed using photoluminescence (PL) spectroscopy. Furthermore, the formation mechanism of nanowires and nanopillars was discussed. Nanowires grew following the vapor-liquid-solid (VLS) mechanism, whereas nanopillars grew following the solid-liquid-solid (SLS) mechanism. These studies provide additional opportunities for the controlled preparation and large-scale production of InP nanomaterials.
摘要:Quantum cascade laser(QCL) is a good laser source in the mid-infrared and far infrared spectrum, which has many advantages such as small size, light weight and high wall plug efficiency. It has important application prospects in sensing, communication and national defense. Metal-organic chemical vapor deposition (MOCVD) technology, as a more efficient epitaxy method, and MOCVD epitaxy growth technology suitable for QCL should be developed to meet the rapidly growing market demand. This paper reported a QCL with full structure epitaxial by MOCVD technology. By modifying the traditional “double-phonon resonant” to “single-phonon continuum depopulation” active region structure, the temperature characteristics of the device are improved and heat escape of electrons are reduced. According to this active region strcture, the doping concentration in the active region is changed to compare the influence of different doping concentrations on the performance of the device. The higher doped active region device with a cavity length of 8 mm and an average ridge width of about 6.7 μm has an optical power of 3.43 W, a central wavelength of about 4.6 μm, and a wall plug efficiency of 13.1% with continuous-wave mode at 20 ℃. The lower doped active region device with a cavity length of 8 mm has an optical power of 2.73 W, a central wavelength of about 4.5 μm, a threshold current of only 0.56 A, and a peak wall plug efficiency of 15.6% with continuous-wave mode at 20 ℃. The output power and wall plug efficiency of devices are significantly improved compared with the QCL epitaxial MOCVD reported in previous articles. The results show that MOCVD technology is fully capable of growing high-power QCL, which is of great significance to promote the technological progress of QCLs.
关键词:Quantum cascade laser;mid-infrared;high-power;metal-organic chemical vapor deposition(MOCVD)
摘要:In order to improve the hole injection efficiency of GaN based multiple quantum wells LED by utilizing V-pits, mini-LEDs with different structures of last quantum barrier (LQB) layer were fabricated. The LQB structures of the four samples are GaN(10 nm), AlN(10 nm), Al0.14Ga0.86N(10 nm), and GaN(8.6 nm)/AlN(1.4 nm), respectively. The recombination mechanisms were studied in these samples with low-temperature electroluminescence spectra, and further validations were carried out through current voltage characteristics testing. The results indicate that a larger proportion of holes transported to deeper quantum wells in samples with AlGaN or GaN/AlN LQB. Experimental results show that the main reason of this improvement is the increasing proportion of holes injected through sidewall quantum wells of V-pits due to the suppression of hole injection through the c-plane MQWs, thereby enhancing hole injection efficiency. LEDs with GaN/AlN LQB exhibit lower forward voltage and higher luminous efficiency. On the other hand, a larger V-pits transport ratio can increase the non-radiative recombination rate, whereas limits the efficiency of samples with AlGaN LQB. We conducted a detailed study on the carrier transport mechanisms and the roles of V-pits in GaN based LED devices.
摘要:Traditional high-speed 100 G lasers are generally by rectangular kovar alloy shells, also known as BOX packaging, which has high cost. Emerging single-wavelength 100 G lasers are gradually adopting coaxial packaging, which can reduce material costs by about 50%. However, due to the integrated refrigerator inside the coaxial package and the use of a single lens solution, there are tolerances for the above two in mass production. There are tolerances and uncertainties in the optical path control, resulting in differences in the size and structure of the laser’s appearance. This leads to matching issues during the assembly of the later optical modules, resulting in higher defect rates and higher costs of batch production control. In this study, the relationship between laser length and positional tolerance was analyzed through theoretical analysis and ZMAX simulations. The coupling efficiency was discussed in relation to the trends and control methods of laser length and positional tolerance. Experimental verification of laser packaging was conducted based on the theoretical analysis and simulation results. Furthermore, control methods and solutions for laser length and positional tolerance were proposed, which have guiding significance for improving laser coupling efficiency, reducing costs, and increasing production efficiency in actual batch production.
摘要:The InAs/GaSb type-Ⅱ superlattice (SL) constitutes the fundamental structure for mid-infrared optoelectronic devices, characterized by its type-Ⅱ band alignment that facilitates the spatial separation of electrons and holes across the interface, and a unique atomic configuration leading to a rich variety of interface states. Building upon the Burt-Foreman envelope function theory, we investigate the influence of different interface states on the electronic states and wave functions of the superlattice. Theoretical calculations indicate that both asymmetric distributions of interface states, namely gradual interface variation and interface potential, result in spin splitting of the heavy-hole band, while spin splitting in the light-hole band occurs only with the application of an interface potential. Additionally, we examine the trends in the band gap of the superlattice system when altering well width and barrier height. The results show that as the barrier thickness increases, the gap calculations under both abrupt and gradual interface states gradually decrease, converging with increasing thickness. In contrast, the gap calculated with interface potential treatment increases with the thickness of the barrier, exhibiting an opposite trend to the former two. This provides a theoretical foundation for the precise design of mid-infrared superlattice devices.
关键词:antimonide;superlattice;interface state;Forward and backward difference method
摘要:In recent years, upconversion nanomaterials have been rapidly developed in the field of food safety detection. Upconversion nanoparticles (UCNPs) can convert near-infrared light into visible light and have the characteristics of low fluorescent background and good chemical stability, improving the sensitivity and accuracy of detection. This review summarizes the current commonly used UCNPs surface functionalization strategies, outlines the recent research progress of UCNPs in food safety detection, discusses some problems and challenges faced by UCNPs in practical application, and looks forward to the future development prospects of UCNPs in food safety detection.
摘要:In this paper, using the MOFs material of MIL-96 as the carrier, allyl fluorescein as the fluorescent group, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the crosslinking agent, azobisisobutyronitrile as the initiator, a novel surface molecularly imprinted fluorescence sensor (MIL-96@AF-SMIPs) for the detection of Rhodamine B was prepared by precipitation polymerization. The sensor was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction, which proved the surface molecularly imprinted fluorescence sensor has been successfully synthesized. In the detection of Rhodamine B, the fluorescence intensity ratio I580/I522showed a good linear relationship with the concentration of Rhodamine B in the range of 0-0.5 μmol/L (R2=0.999). The detection limit was 8.03 nmol/L. In addition, the sensor exhibited high selectivity, good reusability and excellent fluorescence stability. The recovery of Rhodamine B in real sample analysis was 94.23%-109.07%, and the relative standard deviation was less than 3.75%. This study provides a feasible method for efficient and rapid detection of Rhodamine B.
关键词:fluorescein;molecularly imprintied;fluorescence detection;rhodamine B
摘要:Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant, which has the characteristics of biotoxicity, high stability and wide distribution, which is a great threat to human health and safety. Therefore, the detection of PFOS is of great significance. In this paper, a tetraphenylvinyl derivative fluorescent probe (TPE-py) was prepared by simple synthesis for the detection of PFOS. The molecular structure, photophysical property, detection effect and sensing mechanism were studied by means of NMR spectroscopy, fluorescence spectrum and ultraviolet-visible absorption spectrum. The results show that TPE-py was successfully prepared and it can detect PFOS quickly and quantitatively based on the properties of electrostatic interaction and aggregation-induced emission by turn-on mode and the detection limit is 0.11 µmol/L.
摘要:Multi-functional textiles with directional moisture management and antibacterial capabilities have the potential to enhance wearer comfort. Existing methods usually physically dip the antibacterial agents onto the surface of hydrophilic textile, which can play a short-term antibacterial effect, but will lead to a large number of burst release of antibacterial agents, cause skin discomfort, and quickly weaken the antibacterial ability. In this study, a photosensitizer-doped self-pumping textile was prepared by electrospinning for directional sweat removal and antibacterial. Specifically, the self-pumping fabric consists of a hydrophobic polyvinylidene-hexafluoropropylene fiber and a hydrophilic alkali hydrolyzed cellulose acetate (CA) fiber. Besides, the polythiophene photosensitizer with high reactive oxygen species production capacity was doped into hydrophilic fiber enabling daylight antibacterial activity. In the contact angle conductance liquid transport model, we confirmed that the liquid transport time increases with the thickness of the hydrophobic, and when the electrospinning time for the hydrophobic layer was 60 s, water could permeate through it to hydrophilic layer in a unidirectional manner within 10 s. Furthermore, antibacterial experiments demonstrated that over 95% of S.aureus and E.coli were eradicated within 10 minutes under xenon lamp irradiation simulating natural light power (25 mW/cm2). This work presented a novel approach for designing functional fabrics.