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Suggestions on Efficiency Droop of GaN-based LEDs
摘要： InGaN/GaN-based light-emitting diodes (LEDs) are widely used in modern society and industry among different areas. However, InGaN/GaN LEDs suffer from an efficiency droop issue: The internal efficiency decreases during high current injection. The efficiency droop significantly affects the development of GaN-based LEDs devices in efficiency and light-output areas. Therefore, the improvement of the droop phenomenon has become a significant topic. This paper introduces several possible mechanisms of droop phenomenon based on different hypotheses including Auger Recombination, Carrier Delocalization and Electron Leakage. Furthermore, some proposals to mitigate efficiency droop, including semipolar LEDs, electron blocking layer(EBL), quaternary alloy and chip design will be discussed and analyzed. Also, it will provide some suggestions for the further optimization of droop phenomenon in each proposal.
关键词： electron blocking layer,semipolar LEDs,GaN-based LEDs,Auger Recombination,chip design,quaternary alloy,Carrier Delocalization,Electron Leakage,efficiency droop
更新于2025-09-23 15:21:01
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Polarization-engineered AlGaN last quantum barrier for efficient deep-ultraviolet light-emitting diodes
摘要： The AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) has been identified as a prospective mercury-free UV source. However, the observation of severe electron overflow and low hole injection efficiency in the conventional DUV LED deteriorates the device performance, attributing to the downward band bending as a result of the strong polarization-induced electric fields between the last quantum barrier (LQB) and the electron blocking layer (EBL). In this study, a composition-graded AlGaN layer with linearly increasing of Al composition from 0.5 to 0.65 is proposed to act as the LQB, replacing the conventional flat LQB to reduce the effective barrier height for hole injection while improving the electron blocking ability. Hence, a considerable enhancement of the output power can be obtained. Moreover, further investigations show that the thickness of graded LQB determine the band bending in the LQB and thus significantly suppress the electron leakage, eventually leading to a boosted output power. The thorough investigation on the LQB could pave the way towards the realization of efficient DUV LEDs of the future.
关键词： electron blocking layer,ultraviolet light-emitting diodes,light output power,polarization field,graded last quantum barrier
更新于2025-09-23 15:19:57
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Highly Efficient Quantum Dot Light‐Emitting Diodes by Inserting Multiple Poly(methyl methacrylate) as Electron‐Blocking Layers
摘要： This work presents a new device architecture integrating multiple poly(methyl methacrylate) (PMMA) electron-blocking layers (EBL) in quantum dot light-emitting diodes (QD-LEDs). The device utilizes red-emitting CdSe/ZnS QD with a novel structure where multiple PMMA EBLs are sandwiched between a pair of QD layers. A systematic optimization of QD-LED structures has shown that a device including two PMMA and three QD layers performs the best, achieving a current efficiency of 17.8 cd A?1 and a luminance of 194 038 cd m?2. Numerical simulation of a simplified model of the proposed QD-LED structure verifies that the structure consisting of two PMMA and three QD layers provides significant improvement in electroluminescent intensity. The simulation provides further insight into the origin of the effect of the PMMA EBL by showing that the addition of PMMA EBL reduces the electron leakage from the active QD region and enhances electron confinement, leading to an increased electron concentration in the QD active layers and a higher radiative recombination rate. The experimental and theoretical studies presented in this work demonstrate that multiple layers of PMMA can act as efficient EBLs in the fabrication of QD-LEDs of improved performance.
关键词： simulation,device architecture,electron-blocking layer,electron leakage,poly(methyl methacrylate) (PMMA),quantum dot light-emitting diodes (QD-LED)
更新于2025-09-19 17:13:59
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Suppression of efficiency droop in AlGaN based deep UV LEDs using double side graded electron blocking layer.
摘要： We have envisaged and designed a novel III-V Nitride based deep ultraviolet light emitting diodes (DUV LEDs) with reasonably high efficiency at higher current density using a double-side grading in electron blocking layer (EBL). Double-side step- and linear-grading in EBL yield better performance attributable to improved hole injection, stifled electron overflow and diminished electrostatic field in the active region. The performance curves indicate that double sided linear grading in EBL has 5.63 times enhancement in power compared to the conventional LED and the efficiency droop is as low as 15% at the current density of 200 A/cm2 for the emission wavelength of ~273 nm.
关键词： Double side compositional grading,Electron Blocking Layer (EBL),Internal Quantum Efficiency (IQE),Deep Ultraviolet (DUV) LEDs
更新于2025-09-19 17:13:59
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Band engineering of III-nitride-based deep-ultraviolet light-emitting diodes: A review
摘要： III-nitride deep ultraviolet (DUV) light-emitting diodes (LEDs) are identified as the promising candidate for energy-efficient, environment-friendly and robust UV lighting source in the application of water/air purification, sterilization, and bio-sensing. However, the state-of-art DUV LED performance is far from satisfaction for commercialization owing to its low internal quantum efficiency, large current leakage and efficiency droop at high current injection, etc. Extensive efforts have been devoted to properly designing the band structures of such luminescent devices to enhance their output power. In this review, we summarize the recent progress on various energy band designs and engineering of DUV LEDs, with particular of interest is paid on the various approaches in band engineering of the electron-blocking layer, quantum well, quantum barrier and the implementation of many novel structures such as tunnel junctions, ultrathin quantum heterostructures to enhance their efficiency. Those inspirational approaches pave the way towards the next generation of greener and efficient UV sources for practical applications.
关键词： Quantum well,Quantum barrier,Deep ultraviolet light-emitting diode,Ultrathin quantum heterostructures,Band engineering,Electron-blocking layer,Tunnel junctions,III-nitride
更新于2025-09-19 17:13:59
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High-Intensity CsPbBr <sub/>3</sub> Perovskite LED using Poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) as Hole Transport and Electron-Blocking Layer
摘要： The majority of highly efficient perovskite light-emitting diodes (PeLED) contain PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) as hole transport layer (HTL). However, the hygroscopic and acidic nature of PEDOT:PSS may lead to deterioration of PeLED performance. Moreover, due to its inferior electron-blocking properties, an additional electron-blocking layer (EBL) is required to establish charge balance and consequently obtain superior emission characteristics in typically electron-rich PeLED structures. In this work, PTAA (poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)) serving both as HTL and EBL is employed to substitute PEDOT:PSS in PeLED. The perovskite CsPbBr3 is chosen as emissive layer (EML) material due to its high color purity and photoluminescence (PL) quantum yield. Dense CsPbBr3 films are fabricated on PTAA-coated ITO substrates by employing a one-step spin-coating approach based on nonstoichiometric perovskite precursor solutions. To suppress non-radiative recombination, a small amount of methylammonium bromide (MABr) is incorporated in the CsPbBr3 lattice. The resulting films exhibit excellent coverage and PL intensity. PeLED containing pure CsPbBr3 films as EML show a green emission with a peak at 520 nm, maximum luminance of 11,000 cd/m2, an external quantum efficiency (EQE) of 3.3 % and a current efficiency (CE) of 10.3 cd/A. Further enhancement to 21,000 cd/m2, 7.5 % and 27.0 cd/A is demonstrated by PeLED with MABr-doped CsPbBr3 layers.
关键词： PTAA,perovskite light-emitting diodes,PEDOT:PSS,electron-blocking layer,CsPbBr3,hole transport layer
更新于2025-09-16 10:30:52
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Enhanced photocurrent in organic photodetectors by the tunneling effect of a hafnium oxide thin film as an electron blocking layer
摘要： To achieve high detectivity of organic photodetectors (OPDs), we investigated hafnium oxide (HfO2) as an electron blocking layer in an attempt to obtain a low leakage current and high photocurrent by the tunneling effect. The prepared devices consisted of indium tin oxide (ITO)/HfO2/(poly(3-hexylthiophene-2,5-diyl)[P3HT]:PC60BM)/Yb/Al. To explore the tunneling effect in a hafnium oxide thin film, we fabricated a thin film using successive ionic layer deposition. The results for hafnium oxide were compared with those for aluminum oxide and poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT:PSS). We found that hafnium oxide results in a low leakage current and high photocurrent owing to the tunneling effect in the OPDs. The resulting detectivity of 1.76 × 1012 Jones for a film thickness of 5.5 nm and bandwidth of ～100 kHz is suitable for commercialization.
关键词： detectivity,tunneling effect,organic photodetectors,hafnium oxide,electron blocking layer
更新于2025-09-16 10:30:52
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Study on electronic blocking layer of 403 nm GaN-based vertical cavity surface emitting lasers
摘要： In order to obtain good optical characteristics in the GaN-based vertical-cavity surface-emitting laser (VCSEL), different kinds of AlGaN electron blocking layers (EBL) were introduced. These were inserted coherently near the active region to limit electron leakage into the p-doped side. The research was conducted by photonic integrated circuit simulator in three-dimensional (PICS3D). The simulated results reveal that an EBL can improve the optical characteristics of a VCSEL effectively. All the advantages are due to a reduction in the electron leakage in the quantum wells. While the voltage of the five-layer EBLs LD is lower than the voltage of the seven-layer EBLs LD, the output power of the two is approximately the same, so the five-layer EBLs is the best choice for comprehensive structure analysis as the epitaxial structure can be grown more easily on it.
关键词： PICS3D,optical characteristics,GaN-based VCSEL,electron blocking layer
更新于2025-09-12 10:27:22