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Novel design strategy for GaAsa??based solar cell by application of singlea??walled carbon nanotubes topmost layer
摘要： Attempts to improve solar cells efficiency touch all its constituents and are directly related to their fabrication protocols. While the most promising material platform for high efficiency photovoltaic devices is still III-V semiconductors, introduction of novel materials like single-walled carbon nanotubes (SWCNTs), which are characterized by unique combination of conductivity and transparency, might greatly yield the device performance. Here, for the first time, we present the results of the fabrication and characterization of a thin-film GaAs solar cell with a SWCNT top contact. We examine the contact between the SWCNT film and the semiconductor structure by means of the optical and electron beam-induced current techniques. The fabricated device demonstrates better performance, that is, increased power conversion efficiency from 10.6% to 11.5% when compared to the cell with the traditional metal contact grid, stemming from the enhanced photocurrent collection efficiency and low parasitic light absorption in the emitter layer. We envision future prospects to exploit the multifunctionality of the SWCNTs in fabrication of highly efficient photovoltaic devices including flexible solar cells.
关键词： EBIC,EQE,solar cell,GaAs,SWCNT,OBIC
更新于2025-09-23 15:21:01
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Highly Stable Red Quantum Dot Light Emitting Diodes with Long T <sub/>95</sub> Operation Lifetime
摘要： Quantum dot light-emitting diodes (QLEDs) with excellent performances such as external quantum efficiency (EQE) and lifetime have almost met the requirement of low brightness display. However, the short operation lifetime under high brightness limits the application of QLEDs in outdoor displays and lightings. Herein, we report a highly efficient, stable red QLED by using of lithium and magnesium co-doped as well as magnesium oxide shell-coated zinc oxide nanoparticle layer as electron transport layer (ETL). The optimized QLED has a high peak EQE of 20.6%, a low efficiency roll-off at high current, and a remarkably long lifetime T95 > 11000 h at 1000 cd m-2, which indicates the realization of the most stable red QLED up to now. The improvement in the long-term stability of the QLED is attributed to the use of co-doped and shell-coated zinc oxide ETL with reduced electron injection to improve the charge balance in device.
关键词： EQE,QLEDs,electron transport layer,ETL,magnesium oxide shell-coated zinc oxide,Quantum dot light-emitting diodes,external quantum efficiency,lithium and magnesium co-doped,ZLMO@MO,lifetime
更新于2025-09-23 15:21:01
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Higha??efficiency quantum dot lighta??emitting diodes with blue cadmiuma??free quantum dots
摘要： We report outstanding electroluminescence properties of high-efficiency blue cadmium-free quantum dot light-emitting diodes (QD-LED). External quantum efficiency (EQE) of 14.7% was achieved for QD-LED emitting at 428 nm. Furthermore, we developed high-efficiency and narrow wavelength emission zinc selenide (ZnSe) nanocrystals emitting at 445 nm and achieved QD-LED with an EQE of 10.7%. These new QDs have great potential to be used in next-generation QD-LED display with wide color gamut.
关键词： cadmium-free,blue quantum dot,QD-LED,EQE
更新于2025-09-23 15:21:01
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Synthesis of emission tunable AgInS <sub/>2</sub> /ZnS quantum dots and application for light emitting diodes
摘要： Indium-rich environmentally-friendly quantum dots (QDs) have received widespread attention due to the absence of cadmium. In this paper, AgInS2 (AIS) QDs are synthesized by hot injection method. By adjusting the ratio of indium/silver (In/Ag=1, 2, 3, 4, 5), the AIS QDs exhibit a blue shift from 868 nm to 603 nm with the indium composition increases. Therein, the AIS QDs with the ratio of In/Ag = 4 show a highest photoluminescent (PL) quantum yields (QYs) up to 57%. AIS QDs are coated with ZnS shell to passivate the surface defects, and the PL QYs of obtained core/shell AIS/ZnS QDs is increased to 72%. By using these AIS/ZnS QDs as light emitters, light emitting diodes are assembled with a stacked multi-layer structure ITO/PEDOT:PSS/Poly-TPD/QDs/ZnO:Mg/Al. The resulted electroluminescent (EL) device exhibits a maximum external quantum efficiency (EQE) of 1.25% and an open circuit voltage of 4.6 V corresponding to a maximum brightness of 1120 cd/m2. Although the performances of the as fabricated AIS/ZnS-based device lag much behind than those of the Cd-based ones, they are expected to be enhanced with much more studies on the synthesis of the QDs and the optimization of device structure.
关键词： Quantum dots,EQE,Light-emitting diodes
更新于2025-09-23 15:19:57
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Red, Green, and Blue Microcavity Quantum Dot Light-Emitting Devices with Narrow Line Widths
摘要： Colloidal quantum dots (QDs) are tiny particles produced chemically from semiconductor materials with sizes below 100 nm. Because of the quantum size effect, QDs have very unique luminescent properties. Based on these light emitters, quantum dot light-emitting diodes (QLEDs) exhibit outstanding electroluminescence (EL) performances and they are promising for application in displays, light sources and quantum-optoelectronic technologies. One of the greatest challenges in QLEDs is their low light outcoupling efficiency due to their planar structure, which limits the external quantum ef?ciency (EQE) of QLEDs for commercial applications. Here, we report the development of a set of red, green, and blue QLEDs with high EQE by incorporating microcavity structure in the devices. These microcavity devices exhibit modified EL spectra with full width at half maximum of 12-14 nm. Red, green, and blue microcavity QLEDs show maximum current efficiency and maximum EQE of 96.5 cd·A-1 and 33.1%, 102 cd·A-1 and 24.7%, and 2.91 cd·A-1 and 11.2%, respectively. We anticipate that a suitable design of a microcavity combining superior QDs will lead to excellent EL performance of QLEDs for displays, ideal QLED-based single-photon sources for quantum information technology, and electrically pumped QD lasers.
关键词： EQE,narrow linewidth,QLED,quantum dot,microcavity,electroluminescence
更新于2025-09-23 15:19:57
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Efficiency improvement of GaAs Quantum Dot in GaAs1-xPx matrix for solar cell applications
摘要： In this paper, we present simulations and the optimization of electrical and optical properties of GaAs Quantum Dots (QD) in a GaAs1-xPx matrix. Our results showed that 25 GaAs/GaAs1-xPx QD layers provide a relative enhancement of 41.34 % and 75.40 % of the short-circuit current and efficiency, respectively. With the same number of the QD layers, the External Quantum Efficiency (EQE) measurement shows that the absorption range edge of low energy photons has been extended from 875 to 1200 nm (?EQE= 25%). The temperature effect has been studied for a different number of QD inserted. The optimal conversion efficiency of 25 QD layers is degraded from 23.50% to 18.70 % by increasing the temperature from 273 K to 350 K. Moreover, the electrical features obtained and EQE measurements for GaAs/GaAs1-xPx QDSC have been compared with those obtained for In0.47Ga0.53As/GaAs0.86P0.14 QDSC, In0.167Ga0.53As/GaAs and GaAs reference cell, in order to show the better structure.
关键词： Quantum dot,solar cells,temperature effect,EQE
更新于2025-09-19 17:13:59
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Reliability investigation on CdTe solar cells submitted to short-term thermal stress
摘要： In this paper, we investigate the effect of short-term thermal stresses in CdTe thin film solar cells. The CdTe solar cells under test are manufactured with physical vapour deposition on soda lime glass in superstrate configuration. Different characterization techniques were used to study the reliability of the solar cells. In particular, external quantum efficiency (EQE) and electroluminescence (EL) measurement were applied in order to investigate the physical processes responsible for degradation. Through this analysis, we give a broad overview of degradation effects using both electrical and optical measurement and correlating the results. We show that (i) during short-term thermal stresses a soft degradation occurs, (ii) the series resistance of the cells increases and (iii) degradation is preliminarily ascribed to the generation of crystal defects due to the diffusion of copper or oxygen atoms in the CdTe solar cells.
关键词： degradation,EL,reliability,CdTe solar cells,EQE,thermal stress
更新于2025-09-16 10:30:52
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Organic light-emitting diodes with split recombination zones: A concept for versatile color tuning
摘要： White organic light emitting diodes (WOLEDs) for general lighting applications are still mostly considered as a possibility rather than a definitive next step in solid-state lighting technology. Vacuum deposited WOLEDs usually run into troubles of complicated manufacturing processes, incompatible emitters, high-precision requirements for emitting layer structuring and monolithic integration. In this work we present a simple method of achieving white emission from a single-stack OLED with three (red, green and blue) emitters utilizing a laterally structured shadow mask. Only the green emitter is deposited via this mask without any alignment requirements, allowing the decoupling of recombination zones for achieving simultaneous emission from all emitters, circumventing the need of additional charge generating layers or vacuum-breaking structuring steps. A highly tunable white emission is demonstrated, irrespective of charge transporting systems or green emitters used. The resulting WOLEDs show external quantum efficiencies and luminous efficacies up to 14% and 26 lm/W, respectively, with CIE coordinates of (0.40, 0.40) and CRI values of up to 80.
关键词： TADF,WOLED,EQE,phosphorescence,recombination zone,OLED
更新于2025-09-16 10:30:52
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Ultraefficient Green LEDs Using Quantum Dots in Liquid Matrix
摘要： Green spectral range, which has the highest human eye sensitivity, is one of the most fundamental colors in lighting and display. Quantum dots (QDs) offer exceptional optical properties including high quantum yield (QY), strong absorption, and narrow emission linewidths for efficient green-emitting diodes. In this article, we demonstrated QD-based light-emitting diodes (QD-LEDs) that operate at a luminous efficiency (LE) level of 95 lumens per electrical watt, the luminous efficacy of optical radiation of 409 lumens per optical watt, and external quantum efficiency (EQE) of 23.3% in the green spectral region. For that, we synthesized 1-octanethiol-capped CdSe/ZnS QDs with an absolute QY of 91% and integrated them in a liquid matrix that allows conservation of the QD efficiency in device architecture. Our simulations were in agreement with the performance of the fabricated QD-LEDs, and they showed that the QD-LEDs can be further improved to reach LE levels over 250 lm/W.
关键词： light-emitting diodes (LEDs),luminous efficiency (LE),liquid-state integration,quantum dots (QDs),External quantum efficiency (EQE)
更新于2025-09-12 10:27:22
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Inside or outside: Evaluation of the efficiency enhancement of OLEDs with applied external scattering layers
摘要： Improving the efficiency of organic light-emitting diodes (OLEDs) by enhancing light outcoupling is common practise and remains relevant as not all optical losses can be avoided. Especially, externally attached scattering layers combine several advantages. They can significantly increase the performance and neither compromise the electric operation nor add high costs during fabrication. Efficiency evaluations of external scattering layers are often done with lab scale OLEDs. In this work we therefore study different characterization techniques of red, green and blue lab scale OLEDs with attached light scattering foils comprising TiO2 particles. Although we observe an increased external quantum efficiency (EQE) with scattering foils, our analysis indicates that areas outside the active area have a significant contribution. This demonstrates that caution is required when efficiency conclusions are transferred to large area applications, for which effects that scale with the edges become less significant. We propose to investigate brightness profiles additionally to a standard EQE characterizations as latter only work if the lateral scattering length is much smaller than the width of the active area of the OLED. Our results are important to achieve more reliable predictions as well as a higher degree of comparability between different research groups in future.
关键词： external scattering layers,efficiency enhancement,OLEDs,EQE,light outcoupling
更新于2025-09-12 10:27:22