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Nondestructive Evaluation of Multijunction Solar Cells for Matching Currents
摘要： Nondestructive methods determining current mismatched ratios in a multijunction solar cell were proposed in view of a compensated concept of subcell’s current. Various compensated lights were employed to determine key CMMR of InGaP-InGaAs-Ge related triple-junction (3J) solar cells. When a 405 nm compensated light is used, short-circuit currents of 9.37 mA/cm2 and 10.28 mA/cm2 were determined for the InGaP-subcell and InGaAs-subcell, respectively, resulting in a CMMR of 4.4%. Excellent agreement in evaluated properties was obtained when a 532 nm, a 638 nm, and 808 nm compensated lights were used. A 3J solar cell fabricated with an anti-reflected coating was also evaluated. Measured results reveal that an overall short-circuit current of 13.5 mA/cm2 is still limited by the InGaP-subcell, resulting in a conversion efficiency of 27%. Together with determined short-circuit current of 15.5 mA/cm2 for the InGaAs-subcell, a possible optimum conversion efficiency of 29.11% is expected.
关键词： solar cell,quantum efficiency,subcell,current-match,Conversion,multijunction
更新于2025-09-11 14:15:04
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Near-infrared polymer light-emitting diodes based on an inverted device structure
摘要： Near-infrared polymer light-emitting diodes (NIR-PLEDs) possess great potential in applications ranging from night-vision device to optical communications. Here we obtained NIR emission from normal red fluorescent polymers by using an inverted device structure with the aid of micro-cavity effects. By tuning the thickness of the emissive layer, the inverted NIR-PLED based on PPF-FSO15-DHTBT10 and MEH-PPV got a near-infrared emission with the main peak located at 700 nm and 706 nm, and the maximum external quantum efficiency (EQEmax) of 0.54% and 1.03%, respectively. The increase of emissive layer thickness caused the relative variation of recombination area, which led to the widely controlling of EL spectra in the inverted device. These results reveal that tuning EL spectrum utilized by inverted device structure would be a promising method to realize near-infrared emission.
关键词： emissive layer thickness,micro-cavity effects,inverted device structure,Near-infrared polymer light-emitting diodes,external quantum efficiency
更新于2025-09-11 14:15:04
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Two-Color Photodetector for the Visible Spectral Range Based on ZnSe/ZnS/GaAs Bragg Reflector
摘要： Effect of the ZnSe/ZnS/GaAs distributed Bragg reflector (DBR) on the parameters of the spectral response of a photodiode based on rectifying contacts in the metal–semiconductor–metal (MSM) system is studied. The calculated photoreflection spectra of the ZnSe/ZnS/GaAs heterostructure are in good agreement with the experimental data. It is shown that the MSM diode provides two-color response of the photodetector at wavelengths of 420 and 472 nm, a sharp decrease in the photosensitivity in the long-wavelength part of the response signal, high quantum efficiency (53%), and low dark current (5 × 10–10 A). It is demonstrated that the narrow-band two-color response of the detector can be tuned to the desired wavelength using appropriate selection of the parameters of the heterostructure that forms that Bragg reflector.
关键词： two-color photodetector,quantum efficiency,MSM diode,distributed Bragg reflector,ZnSe/ZnS/GaAs
更新于2025-09-11 14:15:04
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Human-eyes-friendly white electroluminescence from solution-processable hybrid OLEDs exploiting new iridium (III) complex containing benzoimidazophenanthridine ligand
摘要： This paper primarily deals with the development of highly efficient phosphorescent iridium (III) complex based on benzoimidazophenanthridine as main ligand. The potential of this complex, as phosphorescent emitter for optoelectronic applications, was screened by different methods, including luminescence spectrometry, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry as well as photoelectron emission spectrometry. The possible application of the developed complex in single-colour vacuum-deposited organic light emitting diodes (OLEDs) exhibiting warm orange electrophosphorescence was demonstrated. The device was characterized with CIE1931 colour coordinates of (0.539, 0.459), colour temperature of 2088 K and maximum external quantum efficiency of 17.5 %. Good performance in OLEDs can be partly explained by efficient orange phosphorescence with quantum yield of 60 % at room temperature. This paper also deals with the development of white hybrid solution-processable organic light-emitting devices, exploiting ultralow concentration of newly synthesized iridium (III) complex as phosphorescent dopant in combination with blue fluorescencent emitter(host), and green emitter exhibiting thermally activated delayed fluorescence emitter. It was designed and fabricated by spin coating white hybrid devices, and was characterized by high quality (human-eyes-friendly) electroluminescence achieving CIE1931 coordinates of (0.335, 0.392), colour temperature of 2910K and colour rendering index of 72 as well as high maximum external quantum efficiency of 8.7 %.
关键词： external quantum efficiency,electrophosphorescence,phosphorescent iridium (III) complex,benzoimidazophenanthridine,white hybrid OLEDs,solution-processable,organic light emitting diodes (OLEDs)
更新于2025-09-11 14:15:04
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Watching Space Charge Build up in an Organic Solar Cell
摘要： A method is presented to spatially resolve the space charge region in organic photovoltaics (OPVs) by measuring white-light bias EQE and optical modeling. The method is demonstrated for a model polymer/fullerene blend with imbalanced carrier mobilities. Furthermore, numerical and analytical means are derived to discuss the general thickness limits for OPVs with imbalanced transport.
关键词： thick films,imbalanced charge transport,quantum efficiency,Organic photovoltaics,space charge
更新于2025-09-11 14:15:04
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High Temperature and Power Dependent Photoluminescence Analysis on Commercial Lighting and Display LED Materials for Future Power Electronic Modules
摘要： commercial light emitting diode (LeD) materials - blue (i.e., inGan/Gan multiple quantum wells (MQWs) for display and lighting), green (i.e., inGan/Gan MQWs for display), and red (i.e., Al0.05Ga0.45in0.5p/Al0.4Ga0.1in0.5P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. the spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (pL) spectroscopy. the spontaneous emission Qe was obtained based on a known model so-called the ABc model. this model has been recently used extensively to calculate the internal quantum efficiency and its droop in the III-nitride LED. At 800 K, the spontaneous emission quantum efficiencies are around 40% for blue for lighting and blue for display LED materials, and it is about 44.5% for green for display LED materials. The spontaneous emission QE is approximately 30% for red for display LED material at 800 K. The advance reported in this paper evidences the possibility of improving high temperature optocouplers with an operating temperature of 500 K and above.
关键词： high temperature,LED materials,power electronics,quantum efficiency,photoluminescence
更新于2025-09-11 14:15:04
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Thermal droop in high-quality InGaN LEDs
摘要： Thermal droop is investigated in high-quality InGaN light-emitting diodes (LEDs). To determine whether it is caused by intrinsic variations in recombination or by transport effects, photoluminescence and electroluminescence measurements are compared. The former does not show signs of pronounced thermal droop, with a near-constant internal quantum efficiency and recombination lifetime, regardless of temperature. In contrast, strong thermal droop is observed in the latter, pointing to transport effects as a leading contributor. Finally, high-efficiency LEDs with near-ideal thermal droop are demonstrated.
关键词： Thermal droop,recombination lifetime,electroluminescence,internal quantum efficiency,transport effects,photoluminescence,InGaN LEDs
更新于2025-09-11 14:15:04
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Long wavelength type II InAs/GaSb superlattice photodetector using resonant tunneling diode structure
摘要： We report on a long wavelength type-II InAs/GaSb superlattice photodetector using resonant tunneling diode (RTD) structure. The linewidth of the satellite peak of the x-ray diffraction curve of the as-grown sample is only 15.7 arcsec showing a very high structural quality. The response maximum wavelength of the RTD detector is 7.5 μm and the 50% cutoff wavelength is 9.6 μm at 77 K. The measured QE is 147% at 7.5 μm when the applied bias voltage is 1.45 V and the corresponding responsivity is 8.9 A/W. This unusual QE is attributed to a large gain achieved when the device is under a resonant tunneling condition. The corresponding shot noise limited detectivity D* is 1.2×1010cm · Hz/W at 1.45 V at 77 K.
关键词： long wavelength,InAs/GaSb superlattice,quantum efficiency,resonant tunneling diode,type II
更新于2025-09-11 14:15:04
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Efficient Deep-Blue Electrofluorescence with an External Quantum Efficiency Beyond 10%
摘要： The design of blue fluorescent materials combining both deep-blue emission (CIEy<0.06) and high-efficiency climbing over the typically limited exciton production efficiency of 25% is a challenge for organic light-emitting diodes (OLEDs). In this work, we have synthesized two blue luminogens, trans-9,10-bis(2-butoxyphenyl)anthracene (BBPA) and trans-9,10-bis (2,4-dimethoxyphenyl)anthracene with high photoluminescence quantum yields (PLQYs) of 89.5% and 87.0%, respectively. Intriguingly, we have proposed a strategy to avoid aggregation-caused quenching, which can effectively reduce the undesirable excimeric emission by introducing two host matrices with twisted molecular structure, 9,10-di(naphth-2-yl) anthracene and 10,100-bis-(4-fluorophenyl)-3,30-dimethyl-9,90-bianthracene (MBAn-(4)-F), in the BBPA emission layer. The device containing the EML of BBPA-doped MBAn-(4)-F exhibited a high external quantum efficiency of 10.27% for deep-blue emission with the Commission International de L’Eclairage CIE coordinates of (0.15, 0.05) via the steric effect. Importantly, this represents an advance in deep-blue-emitting fluorescent OLED architectures and materials that meet the requirements of high-definition display.
关键词： external quantum efficiency,deep-blue emission,fluorescent materials,OLEDs,steric effect
更新于2025-09-10 09:29:36
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Synthesis and photophysical properties of europium pentafluorinated β-diketonate complexes
摘要： Two pentafluorinated β-diketone ligands, 4,4,5,5,5-pentafluoro-1-(4-methoxyphenyl)pentane-1,3-dione (PFMP) and 4,4,5,5,5-pentafluoro-1-(4-dimethylaminophenyl)pentane-1,3-dione (PFAP), had been employed to synthesize six novel europium (III) complexes with ancillary ligands 2,2-dipyridine, 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline. The synthesized europium (III) complexes were characterized by FTIR, 1H NMR, UV–Vis, luminescence spectroscopy, elemental analysis and thermogravimetric analysis. The photoluminescence spectra of these complexes showed the typical europium (III) red emissions in solid state and chloroform solution, assigned to 5D0 → 7Fj (j = 0–4) transitions. The higher values of intensity parameter Ω2 indicated that the europium ion was in a highly polarizable ligand field in these complexes. Europium (III) complexes with the β-diketone PFMP exhibited much better photoluminescence properties than complexes with the β-diketone PFAP. Especially, the europium (III) complex of the β-diketone PFMP with the auxiliary ligand 2,2-dipyridine displayed the longest lifetime value, the highest quantum yield and good CIE color coordinates matching the pure red color (x = 0.67, y = 0.33) in these complexes. In addition, the proposed energy transfer mechanisms and the thermal stability of these complexes were also investigated and analyzed.
关键词： Photoluminescence,Europium complex,Quantum efficiency,Luminescent lifetime,Thermal analysis,Pentafluorinated β-diketone
更新于2025-09-10 09:29:36