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Efficient Near‐Infrared Light‐Emitting Diodes based on In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots
摘要： Near-infrared (NIR) lighting plays an increasingly important role in new facial recognition technologies and eye-tracking devices, where covert and nonvisible illumination is needed. In particular, mobile or wearable gadgets that employ these technologies require electronic lighting components with ultrathin and flexible form factors that are currently unfulfilled by conventional GaAs-based diodes. Colloidal quantum dots (QDs) and emerging perovskite light-emitting diodes (LEDs) may fill this gap, but generally employ restricted heavy metals such as cadmium or lead. Here, a new NIR-emitting diode based on heavy-metal-free In(Zn)As–In(Zn)P–GaP–ZnS quantum dots is reported. The quantum dots are prepared with a giant shell structure, enabled by a continuous injection synthesis approach, and display intense photoluminescence at 850 nm with a high quantum efficiency of 75%. A postsynthetic ligand exchange to a shorter-chain 1-mercapto-6-hexanol (MCH) affords the QDs with processability in polar solvents as well as an enhanced charge-transport performance in electronic devices. Using solution-processing methods, an ITO/ZnO/PEIE/QD/Poly-TPD/MoO3/Al electroluminescent device is fabricated and a high external quantum efficiency of 4.6% and a maximum radiance of 8.2 W sr?1 m?2 are achieved. This represents a significant leap in performance for NIR devices employing a colloidal III–V semiconductor QD system, and may find significant applications in emerging consumer electronic products.
关键词： covert,light-emitting diode,illumination,electroluminescence,quantum dots,near-infrared
更新于2025-09-12 10:27:22
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Simulation of Multilayer Energy Efficient OLEDs for Flexible Electronics Applications
摘要： Organic light emitting (OLEDs) work on electro luminescence principles and these OLEDs are commercially available and can be used in display because of the low power consumption. Proposed research deals with the design of high-efficiency OLEDs, including electrical and optical design of OLEDs. The Luminescent efficiency of bilayer and Triple layer OLED experiment and analysis was done using the Silvaco TCAD tool in this research work. The simulation of electronics and optical features such luminescence power versus anode voltage, anode voltage versus anode current characteristics and exciton state of both bilayer and Triple layer OLEDs were discussed. The physical design, processes as well as principles of OLED has been discussed and operational distribution of Langevin recombination inside proposed structures were acquired and discussed.
关键词： Efficiency Improvement,Organic Light emitting diode (OLEDs),Multilayer,TCAD
更新于2025-09-12 10:27:22
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Comparison of Disinfection Performance of UVC‐LED and Conventional Upper‐Room UVGI Systems
摘要： We developed a novel, compact upper-room ultraviolet germicidal irradiation with light-emitting diode sources (UR-UVGI-LED) system to enhance the disinfection of bioaerosols in an enclosed room space. Its effectiveness was evaluated and compared with the conventional upper-room ultraviolet germicidal irradiation system with mercury vapor sources (UR-UVGI-MV). Escherichia coli, Serratia marcescens, and Staphylococcus epidermidis were atomized under the well-mixed condition and exposed to UR-UVGI-LED (or UR-UVGI-MV) device. The intensity output of the UR-UVGI-LED was also varied from 0% (no LED), 25%, 50% to 100% to further evaluate the UR-UVGI-LED disinfection effectiveness under different power levels. The decay rates for UR-UVGI-LED ranged from -0.1420±0.04min-1 to -0.3331±0.07min-1 for Escherichia coli, -0.1288±0.01min-1 to -0.3583±0.02min-1 for Serratia marcescens, and -0.0330±0.01min-1 to -0.0487±0.01min-1 for Staphylococcus epidermidis. It is noticed that the intensity level has a non-linear influence on the UR-UVGI-LED’s performance. The decay rates achieved by the UR-UVGI-MV system were -0.3867±0.08min-1, -0.4745±0.002min-1, and -0.1624±0.02min-1 for Escherichia coli, Serratia marcescens, and Staphylococcus epidermidis, respectively. Hence, the disinfection performance of both UR-UVGI-LED and UR-UVGI-MV systems was comparable for Escherichia coli and Serratia marcescens. These results demonstrate that UR-UVGI-LED has high potential to be used as a safe and effective irradiated light source to disinfect indoor airborne pathogens.
关键词： Airborne pathogens,Upper-room UVGI,Disinfection bioaerosols,Light-emitting diode,IAQ,Ultraviolet C
更新于2025-09-12 10:27:22
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Phthalonitrile-based bipolar host for efficient green to red phosphorescent and TADF OLEDs
摘要： A bipolar host material named 4-(9H-carbazol-9-yl)phthalonitrile (CzPN) was developed by combining carbazole and phthalonitrile as donor and acceptor units, respectively. The introduction of the phthalonitrile unit realized a relatively small energy gap of 3.00 eV as well as a deep lowest unoccupied molecular orbital level of ?2.72 eV. The characterization of carrier-only devices demonstrated the bipolar charge transporting property of CzPN. With a triplet energy of 2.70 eV, CzPN was investigated as host in green, yellow, and red phosphorescent organic light-emitting diodes (PhOLEDs) and green thermally activated delayed fluorescence (TADF) devices. A low turn-on voltage of 2.8 V was achieved by all the four diodes. Both PhOLEDs and TADF devices exhibited high external quantum efficiency values over 20% with relatively small efficiency roll-offs. These findings demonstrate that CzPN is an excellent host material for both phosphorescent and TADF emitters, and phthalonitrile is a promising unit to develop universal host materials.
关键词： Phthalonitrile,Bipolar host,Phosphorescent organic light-emitting diode,Thermally activated delayed fluorescence
更新于2025-09-12 10:27:22
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High-Voltage AlInGaN LED Chips
摘要： A high-voltage light-emitting diode (LED) flip chip based on an AlInGaN heterostructure is developed and fabricated. The LED flip chip consists of 16 elements connected in series, each of which is a conventional LED. The chip with a total area of 1.25 × 1.25 mm is intended for a working current of 20 mA and a forward voltage of 48 V. To improve the current-distribution uniformity over the active region of the chip elements and to minimize the losses of the element area occupied by the n-type contact, the n-type contact pads in them are arranged inside the p-type contact region due to the two-level metallization layout with an intermediate insulating layer of dielectric. The arrangement topology of the contact pads is developed using numerical simulation. An increase in the quantum efficiency of the chip is provided by the application of combinations of metals with a high reflectance at the LED emission wavelength, which are used when fabricating n- and p-type contacts as well as current-carrying strips.
关键词： light-emitting diode,flip-chip design,LED chip,gallium nitride,high-voltage chip
更新于2025-09-12 10:27:22
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Luminescent properties of CaSc2O4:Ce3+ green phosphor for white LED and its optical simulation
摘要： Green-emissive Ce3t-doped CaSc2O4 phosphors were synthesized by solid-state method. The water washing process of the as-prepared samples was several times conducted because of severe hydration of unreacted CaO and CaF2 flux residual. The washed CaSc2O4:Ce3t phosphors showed a single phase with a crystallite size of 1–3 μm, and its photoluminescence intensity was 10% improved compared with the as-prepared. It shows the broad 450 nm excitation peak and the green emission peak at 520 nm with a half width of 105 nm. Its temperature dependence showed the similar thermal stability with a commercial silicate phosphor. The optical simulation and the real fabrication of white LEDs with a combination of our green phosphor and one of possible orange-red phosphors demonstrated that the white LED with Sr3SiO5:Eu2t orange phosphor gives the best luminous efficacy and the appropriate color rendering index of 70 under the daylight color temperature of 6400 K.
关键词： CaSc2O4:Ce3t,White-light-emitting diode,Optical simulation,Photoluminescence,Green emission
更新于2025-09-12 10:27:22
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Gb/s underwater wireless optical communications using series-connected GaN micro-LED arrays
摘要： High speed wireless communications are highly desirable for many industrial and scientific underwater applications. Acoustic communications suffer from high latency and limited data rates, while Radio Frequency communications are severely limited by attenuation in seawater. Optical communications are a promising alternative, offering high transmission rates (up to Gb/s), while water has relatively low attenuation at visible wavelengths. Here we demonstrate the use of series-connected micro-light-emitting-diode (μLED) arrays consisting of 6 μLED pixels either 60 μm or 80 μm in diameter and operating at 450 nm. These devices increase the output power whilst maintaining relatively high modulation bandwidth. Using orthogonal frequency division multiplexing (OFDM) we demonstrate underwater wireless data transmission at rates of up to 4.92 Gb/s, 3.22 Gb/s and 3.4 Gb/s over 1.5 m, 3 m and 4.5 m, respectively, with corresponding bit error ratios (BERs) of 1.5×10-3, 1.1×10-3 and 3.1×10-3, through clear tap water, and Mb/s rates through >5 attenuation lengths (ALs) in turbid waters.
关键词： Underwater wireless optical communications,GaN,micro-light-emitting-diode arrays,turbid waters
更新于2025-09-12 10:27:22
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Carrier transport improvement in ZnO/MgZnO multiple-quantum-well ultraviolet light-emitting diodes by energy band modification on MgZnO barriers
摘要： Ultraviolet (UV) light-emitting diodes (LEDs) based on zinc oxide (ZnO) materials have been the subject of many investigations because of their potential applications. In this study, ZnO/MgZnO multiple-quantum-well UV LEDs with graded-composition barriers were developed and numerically analyzed. The simulation results demonstrate that an optimized LED with a Mg composition graded from 24% to 2% in each triangular barrier exhibits the highest internal quantum efficiency (IQE) (88.0%) at 200 A/cm2, showing a 31.3% increase compared with the conventional LED with square barriers. This enhancement is attributed to the modified energy band structures that improve the symmetry in carrier transportation and increase the radiative recombination rate in each ZnO quantum well, thus enhancing the IQE of the device. Additionally, the different band-offset ratios of the MgZnO/ZnO and InGaN/GaN heterojunctions, which lead to the different carrier transport and electroluminescence properties of the ZnO- and GaN-based LEDs, were discussed here, providing researchers new insights into device design of ZnO-based LEDs.
关键词： Numerical simulation,Quantum barrier,Carrier transport,Zinc oxide,Light-emitting diode
更新于2025-09-12 10:27:22
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38.1: Quantitative Analysis of Charge Transport in Single‐Carrier Devices and OLEDs Combining DC and AC Data
摘要： Single-carrier devices are perfect model systems to extract material parameters for more complex multilayer organic light-emitting diodes (OLEDs) and to learn about charge transport and injection properties of the device. By combining simulation and measurements in steady-state and frequency domain, we obtain a set of reliable material parameters which can be used to model the multilayer OLED structure. Moreover, we can also evaluate the contact behavior and conclude that the OLED operation is limited by electron transport.
关键词： characterization,organic light-emitting diode,mobility,material parameter,doping
更新于2025-09-12 10:27:22
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Advanced Thermoelectric Materials for Energy Harvesting Applications || Thermoelectric Control of Deep UV LED to Improve Optical Performance
摘要： A thermoelectric control system using thermoelectric cooler devices (TEC) combined with an aluminum heat dissipater and a fan heat extractor allows improving considerably the optical performance of deep UV LEDs (285 nm) operating at desired temperatures. A proportional, integral, and differential controller (PID) control technique was implemented to control the voltage in the TEC devices, and therefore, the desired range of temperatures can be achieved. The PID parameters are obtained with computational simulations based on physical models and experimental data recordings of the temperature, using a thermistor sensor for the temperature measurements and SiC photodiode with UV enhanced system for the optical power measurements. The experimental data show that decreasing the temperature of the UV-C LED light source using a TEC increases the optical output power, while it has been shown that the lifetime of the LED devices can be improved.
关键词： thermoelectric cooler,light-emitting diode,optoelectronics,temperature,ultraviolet
更新于2025-09-12 10:27:22