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Organic tandem solar cells with 18.6% efficiency
摘要： Tandem organic photovoltaic (TOPV) cell is one of the technologies to harvest more solar power by staking two or more OPV devices on top of each other. Recently, the highest power conversion efficiency (PCE) ever achieved was 17.3%. Herein, this paper simulates the response of 676 different TOPV devices that consists front and back OPV cells. For this purpose, this paper uses the best 26 single-cell OPV devices to form the TOPV front and back cells combinations. The results show that there are some new TOPVs that can exceed 17.3% efficiency limit for TOPV. Also, in this work thickness optimization was performed for these new TOPV devices with an objective of efficiency maximization. As a result, using PBDTS-TDZ: ITIC in the front cells and PTB7-Th: O6T-4F:PC71BM in the back cell gives 18.6% efficiency. Likewise, the TOPV of PBDB-T-2F:TfIF-4FIC in the front cell with PTB7-Th:O6T-4F:PC71BM in the back cell gives 18.06% efficiency.
关键词： Organic materials,External quantum efficiency,Tandem organic solar cells,Optimization,Simulation
更新于2025-09-16 10:30:52
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The role of photon recycling in perovskite light-emitting diodes
摘要： Perovskite light-emitting diodes have recently broken the 20% barrier for external quantum efficiency. These values cannot be explained with classical models for optical outcoupling. Here, we analyse the role of photon recycling (PR) in assisting light extraction from perovskite light-emitting diodes. Spatially-resolved photoluminescence and electroluminescence measurements combined with optical modelling show that repetitive re-absorption and re-emission of photons trapped in substrate and waveguide modes significantly enhance light extraction when the radiation efficiency is sufficiently high. In this manner, PR can contribute more than 70% to the overall emission, in agreement with recently-reported high efficiencies. While an outcoupling efficiency of 100% is theoretically possible with PR, parasitic absorption losses due to absorption from the electrodes are shown to limit practical efficiencies in current device architectures. To overcome the present limits, we propose a future configuration with a reduced injection electrode area to drive the efficiency toward 100%.
关键词： external quantum efficiency,light-emitting diodes,photon recycling,optical outcoupling,perovskite
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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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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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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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
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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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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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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