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Analysis of dominant non-radiative recombination mechanisms in InGaN green LEDs grown on silicon substrates
摘要： Relationship between the external quantum efficiency (EQE) curves and the dominant non-radiative recombination mechanisms of InGaN green LEDs grown on silicon substrates were investigated. Through the analysis of the ABC+(cid:1)(cid:2)(cid:3)(cid:4) model, the significant drop in EQE at low current levels is due to an increasingly defect-related Shockley-Read-Hall (SRH) recombination. Under extremely low current densities, the defect traps can even become the dominant channel for the leakage current through the tunneling process, thereby reducing the efficiency of carrier injection into the active region. These observations were further supported by the carrier lifetime measurement. However, this fails to explain the droop in EQE at high current densities, especially when SRH recombination has been saturated. Our results show that carrier leakage has becomes dominant at high current density when Auger recombination has been less impossible. Reduced carrier leakage may lead to increased carrier injection efficiency, which in turn alleviates EQE droop.
关键词： silicon substrates,InGaN,non-radiative recombination,green LEDs,external quantum efficiency,carrier leakage
更新于2025-09-19 17:13:59
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Elucidating the origin of external quantum efficiency losses in cuprous oxide solar cells through defect analysis
摘要： Heterojunction Cu2O solar cells are an important class of Earth-abundant photovoltaics that can be synthesized by a variety of techniques, including electrochemical deposition (ECD) and thermal oxidation (TO). The latter gives the most efficient solar cells of up to 8.1% reported in the literature, but is limited by low external quantum efficiencies (EQE) in the long wavelength range (490–600 nm). By contrast, ECD Cu2O gives higher short wavelength EQEs of up to 90%. We elucidate the cause of this difference by characterizing and comparing ECD and TO films using impedance spectroscopy and fitting with a lumped circuit model to determine the trap density, followed by simulations. The data indicates that TO Cu2O has a higher density of interface defects, located approximately 0.5 eV above the valence band maximum (NV), and lower bulk defect density thus explaining the lower short wavelength EQEs and higher long wavelength EQEs. This work shows that a route to further efficiency increases of TO Cu2O is to reduce the density of interface defect states.
关键词： Atmospheric pressure spatial atomic layer deposition,chemical vapour deposition,Interface and bulk defects,Impedance spectroscopy,Cuprous oxide solar cells,Quantum efficiency
更新于2025-09-19 17:13:59
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Industrial Applications of Nanomaterials || Nanomaterials-based UV photodetectors
摘要： Photodetectors are essential elements applied in video imaging, optical communications, biomedical imaging, security, night-vision, gas sensing, and motion detection, which possess the ability to transform light into electrical signals precisely. As the scale and diversity of application areas are growing, the need for innovative photodetection platform technologies with higher performance in terms of speed, efficiency or wavelength range, as well as material flexibility, transparency, and complementary metal-oxide-semiconductor (CMOS) integrability, is becoming more critical. In the past decades, extensive efforts have been devoted to explore the next generation of photodetector materials, such as In2Te3, ZnO, and GaN, with low noise, high photosensitivity, and good stability. However, many of these novel photodetector materials still suffer from limited photocurrent and photoresponse speed.
关键词： Nanomaterials,Schottky contacts,photoconductive gain,photodetection mechanism,photoresistors,linear dynamic range,responsivity,external quantum efficiency,photodiodes,specific detectivity,UV photodetectors
更新于2025-09-19 17:13:59
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Highly efficient blue organic light-emitting diodes based on carbene-metal-amides
摘要： Carbene-metal-amides are soluble and thermally stable materials which have recently emerged as emitters in high-performance organic light-emitting diodes. Here we synthesise carbene-metal-amide photoemitters with CF3-substituted ligands to show sky-blue to deep-blue photoluminescence from charge-transfer excited states. We demonstrate that the emission colour can be adjusted from blue to yellow and observe that the relative energies of charge transfer and locally excited triplet states influence the performance of the deep-blue emission. High thermal stability and insensitivity to aggregation-induced luminescence quenching allow us to fabricate organic light-emitting diodes in both host-free and host-guest architectures. We report blue devices with a peak external quantum efficiency of 17.3% in a host-free emitting layer and 20.9% in a polar host. Our findings inform the molecular design of the next generation of stable blue carbene-metal-amide emitters.
关键词： charge-transfer excited states,photoluminescence,carbene-metal-amides,organic light-emitting diodes,external quantum efficiency
更新于2025-09-19 17:13:59
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Cd2SnO4/CdS/Cu2O/Ag solar cell obtained by chemical techniques
摘要： By first time Cd2SnO4/CdS/Cu2O/Ag heterojunctions were studied for their application in solar cells. The heterostructure was deposited on glass-substrate and obtained by chemical techniques: i) Cd2SnO4 as TCO by sol-gel, ii) CdS as n-layer by chemical bath deposition and iii) Cu2O as p-layer by spray pyrolysis. The thicknesses of the Cd2SnO4 and CdS layers were 290 nm and 135 nm, respectively. Different thicknesses of Cu2O (τ) were used to study the effect of this parameter on the solar cell performance (135, 185, 220, 350 and 800 nm). The best photovoltaic parameters were obtained with τ= 220 nm achieving an VOC=346 mV, JSC=1.57 mA/cm2, FF=33.4 and η=0.18 %. External quantum efficiency shows current generated at energy values below Cu2O and CdS band gaps.
关键词： Cu2O/CdS,chemical techniques,solar cell,quantum efficiency,Spray pyrolysis
更新于2025-09-19 17:13:59
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On the contribution of fullerene to the current of planar heterojunction organic solar cells.
摘要： Recently, significant progress in the field of organic photovoltaic cells was obtained by substituting new electron acceptor molecules to the fullerene, which was attributed to the fact that the fullerene absorption is quite small. Nevertheless, we demonstrate in the present work that, in the case of inverted cells, i.e. when the transparent bottom electrode is used as cathode, the contribution of fullerene to the Jsc short-circuit current of the cells, if not dominant, is not negligible; and that mainly in the short wavelength spectral range. The experimental results are confirmed by an optical simulation. Due to this significant contribution to Jsc, the light transmission of the transparent electrode towards the UV-part of the spectrum is crucial for inverse cell performances. When a transparent conductive electrode based on an alternative dielectric/metal/dielectric structure is substituted to ITO, such as ZnS/Ag/TiO2, the study allows to obtain promising results, although there is a loss of performance due to the decrease of transmission of TiO2 below 400 nm in wavelength.
关键词： Absorption,Optical Modeling,External Quantum Efficiency,Organic solar cells,Planar heterojunction
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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High-performance blue perovskite light-emitting diodes based on the a??far-field plasmonic effecta?? of gold nanoparticles
摘要： Metal halide perovskites have become the next-generation electroluminescent materials due to their excellent optoelectronic properties. In the last several years, there has been tremendous progress in the performance of red and green-light perovskite electroluminescent devices (PeLEDs) with external quantum efficiencies (EQE) exceeding 14% and 21%, respectively. In contrast, blue PeLEDs are still in infancy stage, due to EQEs below 1%. Therefore, development of blue PeLEDs is sorely needed since blue light plays a vital role in achieving full-color and white-light emission. In order to improve the efficiency of blue PeLEDs, herein we introduce gold nanoparticles (Au NPs) into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) to achieve a high performance blue PeLEDs with an emission wavelength ~475 nm. By introducing Au NPs, the optical properties of poly(ethylene oxide) (PEO):PEA2(CsPbBrxCl3?x)n?1PbBr4 perovskite films have been significantly improved leading to 3.8 times enhancement in fluorescence intensity. Based on this improvement, the blue PeLEDs record a maximum luminance and EQE of ~1110 cd/m2 and 1.64%, respectively performing among the best reported so far. Finally, the PeLED performance improvement is attributed to the far-field surface plasmonic effect of Au NPs. This effect is originated from the interference between the original chromophores emission and the mirror-reflected emission of mirror-type substrates. This study not only reveals the function of Au NPs in development of blue PeLEDs, but also offers new insights into the fundamental physics underlying the effect of surface plasmon resonance of Au NPs on perovskite light emitting devices.
关键词： gold nanoparticles,blue PeLEDs,Metal halide perovskites,far-field plasmonic effect,external quantum efficiency
更新于2025-09-19 17:13:59
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Two-dimensional Ruddlesdena??Popper layered perovskite for light-emitting diodes
摘要： Solution-processed metal halide perovskite light-emitting diodes (PeLEDs) have attracted extensive attention due to the great potential application in energy-efficient lighting and displays. Two-dimensional Ruddlesden–Popper (2DRP) layered perovskites exhibit high photoluminescence quantum efficiency, improved film morphology, and enhanced operational stability over their three-dimensional counterparts, making them attractive for high-performance PeLEDs. In addition, 2DRP perovskite materials with a tunable exciton binding energy are suitable for preparing PeLEDs with color-tunability. In this perspective, we first introduce the merits of the 2DRP layered perovskites in terms of their structural characteristics. The progress in 2DRP PeLEDs is then reviewed. The challenges and new opportunities of the PeLEDs are finally discussed. We hope to open up new perspectives for rational designs of the 2DRP perovskite materials for PeLEDs with unprecedented efficiency and stability.
关键词： operational stability,film morphology,photoluminescence quantum efficiency,Two-dimensional Ruddlesden–Popper layered perovskite,color-tunability,light-emitting diodes
更新于2025-09-19 17:13:59
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Penetration in Biological Tissue Using Light-Emitting Diodes with Highly Efficient Near-Infrared ScBO3:Cr3+ Phosphor
摘要： Recently, infrared (IR) light-emitting diodes (LEDs) have attracted considerable interest in the research field worldwide. IR phosphors, the basic materials utilized in LEDs, have become a research hotspot as well. Here, we introduce the high-quantum-efficiency IR ScBO3:Cr3+ phosphor, which provides a spectral range of emission from 700 nm to 1000 nm with a peak maximum at 800 nm. Electron paramagnetic resonance spectroscopy, with high element selectivity, was used to elucidate the unusual small peak in the photoluminescence spectrum. Phonon structure and electron–lattice interaction were well observed and discussed via temperature-dependent measurements. Moreover, the high quantum efficiency of 72.8% was achieved. To evaluate their potential practical application, phosphor-converted LED packages were designed, which revealed high stability and high output power of 39.11 mW. Furthermore, the fabricated IR LED demonstrated remarkable penetration ability toward biological tissues. This study provides insights into the luminescent properties and the practical applications of IR LEDs.
关键词： infrared,light-emitting diodes,biological tissue penetration,phosphors,quantum efficiency
更新于2025-09-19 17:13:59