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Bright high-colour-purity deep-blue carbon dot light-emitting diodes via efficient edge amination
摘要： Deep-blue light-emitting diodes (LEDs) (emitting at wavelengths of less than 450 nm) are important for solid-state lighting, vivid displays and high-density information storage. Colloidal quantum dots, typically based on heavy metals such as cadmium and lead, are promising candidates for deep-blue LEDs, but these have so far had external quantum efficiencies lower than 1.7%. Here we present deep-blue light-emitting materials and devices based on carbon dots. The carbon dots produce emission with a narrow full-width at half-maximum (about 35 nm) with high photoluminescence quantum yield (70% ± 10%) and a colour coordinate (0.15, 0.05) closely approaching the standard colour Rec. 2020 (0.131, 0.046) specification. Structural and optical characterization, together with computational studies, reveal that amine-based passivation accounts for the efficient and high-colour-purity emission. Deep-blue LEDs based on these carbon dots display high performance with a maximum luminance of 5,240 cd m?2 and an external quantum efficiency of 4%, notably exceeding that of previously reported quantum-tuned solution-processed deep-blue LEDs.
关键词： carbon dots,deep-blue LEDs,amine-based passivation,external quantum efficiency,high-colour-purity
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Investigation of Resonant-Cavity-Enhanced GeSn Photodetectors in Short-Wavelength Infrared Regime
摘要： GeSn with a 10% Sn content for resonant-cavity-enhanced photodetectors (RCE PDs) was grown and the RCE PDs was designed for 2000-nm operation, exhibiting a quantum efficiency up to 91%. This work shows RCE GeSn PDs can be a promising route toward high-response SWIR detection.
关键词： Resonant-cavity-enhanced photodetectors,quantum efficiency,GeSn
更新于2025-09-12 10:27:22
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Sensitivity of Sub-bandgap External Quantum Efficiency Measurements of Solar Cells under Electrical and Light Bias
摘要： The measurement of the external quantum efficiency (EQE) for photo-current generation at photon energies below the bandgap of semiconductors has always been an important tool for understanding phenomena such as Urbach tail and trap state dynamics. The shape of the sub-gap EQE can also reveal the subtle but important physics of inter-and-intramolecular states that lay at the heart of charge photogeneration in molecular systems such as organic semiconductors. In this work, we examine the influence of optical and electrical noise on the sensitivity of EQE measurements under different electrical and optical bias conditions and demonstrate how to enhance the dynamic range to an unprecedented >100 dB. We identify and study several apparatus-and-device-related factors limiting the sensitivity including: the electrical noise floor of measurement system; flicker and pick-up noise; illumination source stray light; the photon noise of the light bias source; the electrical noise of the voltage bias source; and shunt-resistance-limited thermal and electrical shot noise of the device. By understanding and minimizing the influence of these factors we are able to detect EQE signals derived from weak sub-gap absorption features in both organic and inorganic solar cell systems at photon energies well below their bandgaps. We area also able to observe sub-gap low finesse cavity interference effects which are sometimes confused with, for example, directly stimulated charge transfer state photo-current.
关键词： Photocurrent spectroscopy,Sub-bandgap absorption,Sensitive external quantum efficiency,Trap states,Solar cells,Charge transfer states
更新于2025-09-12 10:27:22
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Exciplex hosts for blue phosphorescent organic light-emitting diodes
摘要： The host material of organic light-emitting diodes (OLEDs) has been advanced from a single host to a mixed host for high efficiency and long lifetime. Several types of mixed host have been reported in the literature, but the exciplex host has been popular as the mixed host of OLEDs. The exciplex host has been developed mostly for red and green phosphorescent OLEDs, and has upgraded device performances, but it is difficult to develop the exciplex host for blue phosphorescent OLEDs. Recently, several works demonstrated the potential of the exciplex host for blue phosphorescent OLEDs. In this paper, the exciplex host for blue OLEDs is reviewed, and its prospects are presented.
关键词： OLEDs,Exciplex host,quantum efficiency,blue phosphorescent device
更新于2025-09-12 10:27:22
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Performance of polycrystalline GaN based metal-semiconductor-metal (MSM) photodetector with different contact
摘要： This paper describes performance of polycrystalline GaN based metal-semiconductor-metal (MSM) photodetector using different contact; Al, ITO, Ni and Pt. The performance of each photodetector was investigated in term of electrical resistivity (r ), signal-to-noise ratio (SNR), responsivity (R), internal quantum efficiency (η) and temporal responsivity. From the results, Ni is suggested to be a good contact for the photodetector. This is due to diffusion of NixO, formed by residual oxides on the GaN layer, into the Ni contact reduced the resistivity, thereby increasing the electrical conductivity of the photodetector. The photodetector with Ni contact demonstrated significant increase in SNR behavior with increasing bias voltage, while its r value was measured to be 2.02 M?.cm2, and η was 3.13%, 2.36% and 1.52%, at λ = 342 nm, 385 nm and 416 nm, respectively. From the temporal responsivity measurement, the rise time = 1.75 sec, the recovery time = 1.87 sec and the sensitivity = 5840%.
关键词： MSM photodetector,electrical contact,resistivity,internal quantum efficiency and temporal responsivity,signal-to-noise ratio,polycrystalline GaN,responsivity
更新于2025-09-12 10:27:22
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High‐Temperature Optical Characterization of GaN‐Based LEDs for Future Power Electronic Modules
摘要： High-temperature optical analysis of three different InGaN/GaN MQW LED structures (peak wavelength λp = 448nm, 467 nm & 515nm) is conducted for possible integration as an optocoupler emitter in high-density power electronic modules. The commercially available LEDs, primarily used in the display (λp = 467 nm & 515nm) and lighting (λp = 448nm) applications, are studied and compared to evaluate if they can satisfy the light output requirements in the optocouplers at high temperatures. The temperature- and intensity-dependent electroluminescence (T-IDEL) measurement technique is used to study the internal quantum efficiency (IQE) of the LEDs. All three LEDs exhibits above 70 % IQE at 500 K, and stable operation at 800 K without flickering or failure. At 800K, a promising IQE of above 40 % is observed for blue for display (λp = 467 nm) and green for display (λp = 515nm) samples. Blue for light (λp = 448nm) sample shows 24 % IQE at 800 K.
关键词： high-temperature optoelectronics,high-density power modules,optocouplers,quantum efficiency
更新于2025-09-12 10:27:22
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Green emitting Ba1.5Lu1.5Al3.5Si1.5O12: Ce3+ phosphor with high thermal emission stability for warm WLEDs and FEDs
摘要： By hetero-valence substituting Ba2+-Si4+ for Lu3+-Al3+ pair in Lu3Al5O12: Ce3+, a new green phosphor Ba1.5Lu1.5Al3.5Si1.5O12: Ce3+ (BLAS: Ce3+) has been obtained. It crystallizes in garnet structure with space group Ia-3d (230). In the structure, Ba2+ ions are incorporated into both dodecahedral Lu3+ and octahedral Al3+ sites while Si4+ ions only occupy tetrahedral Al3+ sites. Under the blue light irradiation of 450 nm, an intense green light peaking at 520 nm was observed and the PL spectrum can be fitted in two Gaussian components, due to the crystal field splitting of Ce3+ 5d states under D2 symmetry constrains. The optical doping concentration of BLAS: Ce3+ is 6% mol, of which the IQE and EQE are 89.1% and 51.8%, respectively. Furthermore, this sample exhibits an extremely good thermal stability, i.e. the integrated emission intensity is still more than 90% of the initial intensity at 480 K. Then, a w-LED device was fabricated from this new green phosphor BLAS: Ce3+ and commercial red phosphor (Ca,Sr)AlSiN3: Eu2+, which shows a quite high color rendering (Ra = 88.2) and a relatively low color temperature 4772 K. Besides, the phosphor exhibits a stable chromaticity under different acceleration voltages. The phosphor may be promising material for the development of solid-state lighting and display systems.
关键词： quantum efficiency,thermal stability,luminescence,garnet structure,lighting and display
更新于2025-09-12 10:27:22
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An Investigation of Internal Quantum Efficiency of Bifacial Interdigitated Back Contact (IBC) Crystalline Silicon Solar Cell
摘要： In this article, we investigated the internal quantum efficiency (IQE) properties of n-type bifacial interdigitated back contact crystalline silicon solar cells using an IQE mapping system. In the cell structure, high and low IQE values were observed above the emitter and back surface field (BSF) regions. The IQE values above the BSF busbar were drastically reduced due to electrical shading loss. Line scan profiles at different wavelengths showed the detailed distribution of IQE values. The IQE values varied greatly depending not only on the difference between emitter and BSF regions but also on the rear side structure such as the electrode width and the distance between the emitter and BSF regions. On the other hand, the IQE spectra at over 950 nm improved by increasing the light absorbance ratio from the rear side. After module formation, the IQE spectra at short wavelengths were significantly reduced. The IQE properties were obtained from the front and rear sides. The difference in the short-circuit current between front side illumination and rear side illumination was mainly due to optical shading loss and carrier recombination loss at the BSF region. For a high cell efficiency, it is necessary to improve the passivation properties of the BSF region and optimize the electrode design.
关键词： Back contacts,internal quantum efficiency,silicon solar cells
更新于2025-09-12 10:27:22
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Triplet management for efficient perovskite light-emitting diodes
摘要： Perovskite light-emitting diodes are promising for next-generation lighting and displays because of their high colour purity and performance1. Although the management of singlet and triplet excitons is fundamental to the design of efficient organic light-emitting diodes, the nature of how excitons affect performance is still not clear in perovskite2–4 and quasi-two-dimensional (2D) perovskite-based devices5–9. Here, we show that triplet excitons are key to efficient emission in green quasi-2D perovskite devices and that quenching of triplets by the organic cation is a major loss path. Employing an organic cation with a high triplet energy level (phenylethylammonium) in a quasi-2D perovskite based on formamidinium lead bromide yields efficient harvesting of triplets. Furthermore, we show that upconversion of triplets to singlets can occur, making 100% harvesting of electrically generated excitons potentially possible. The external quantum and current efficiencies of our green (527 nm) devices reached 12.4% and 52.1 cd A?1, respectively.
关键词： Perovskite light-emitting diodes,quasi-2D perovskite,external quantum efficiency,triplet excitons,organic cation
更新于2025-09-12 10:27:22
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Synthesis of Alloyed ZnSeTe Quantum Dots as Bright, Color-Pure Blue Emitters
摘要： Considering a strict global environmental regulation, fluorescent quantum dots (QDs) as key visible emitters in the next-generation display field should be compositionally non-Cd. When compared to green and red emitters obtainable from size-controlled InP QDs, development of non-Cd blue QDs remains stagnant. Herein, we explore synthesis of non-Cd, ZnSe-based QDs with binary and ternary compositions toward blue photoluminescence (PL). First, size increment of binary ZnSe QDs is attempted by a multiply repeated growth until blue PL is attained. Although this approach offers a relevant blue color, excessively large-sized ZnSe QDs inevitably entail a low PL quantum yield (QY). As an alternative strategy to the above size enlargement the alloying of high-band gap ZnSe with lower-band gap ZnTe in QD synthesis is carried out. These alloyed ternary ZnSeTe QDs after ZnS shelling exhibit systematically tunable PL of 422?500 nm as a function of Te/Se ratio. Analogous to state-of-the-art heterostructure of InP QDs with a double-shelling scheme, an inner shell of ZnSe is newly inserted with different thicknesses prior to an outer shell of ZnS, where the effects of the thickness of ZnSe inner shell on PL properties are examined. Double-shelled ZnSeTe/ZnSe/ZnS QDs with an optimal thickness of ZnSe inner shell are then employed for all-solution-processed fabrication of blue QD-light-emitting diode (QLED). The present blue QLED as the first ZnSeTe QD-based device yields a peak luminance of 1195 cd/m2, current efficiency of 2.4 cd/A, and external quantum efficiency of 4.2%, corresponding to the record values reported from non-Cd blue devices.
关键词： external quantum efficiency,alloyed ZnSeTe quantum dots,Non-Cd blue emitters,ZnSe inner shell,quantum dot-light-emitting diode
更新于2025-09-11 14:15:04