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Homoleptic mer-Ir(III) complexes for highly efficient solution-processable green phosphorescent organic light-emitting diodes with high current efficiency
摘要： Two new highly efficient homoleptic green-emitting meridional iridium (III) complexes namely, mer-tris[5-hexyl-8-trifluoromethyl-5H-benzo(c)(1,5)naphthyridin-6-one]iridium(III) (mer-Ir1) and mer-tris[5-ethylhexyl-8-trifluoromethyl-5H-benzo(c)(1,5)naphthyridin-6-one]iridium(III) (mer-Ir2) were designed and synthesized at high temperature. These new Ir(III) complexes consist of amide bridged trifluoromethyl substituted phenylpyridine skeleton with longer alkyl chain. Interestingly, both Ir(III) complexes, mer-Ir1 and mer-Ir2 show bright green emission (λmax = 528 nm) with high photoluminescence quantum yields of 42 and 51% in solution at room temperature, respectively. Their thermal, photophysical, electrochemical, and electroluminescent (EL) properties were fully investigated. Both complexes were used as dopants for solution-processed green phosphorescence organic light-emitting diodes (PHOLEDs). Notably, the device using mer-Ir2 as new green dopant exhibited excellent EL performance with a maximum external quantum efficiency of 20.03% and maximum current efficiency of 67.81 cd A-1. To the best of our knowledge, this is the first time, particularly Ir(C^N)3 based mer-Ir(III) isomers showing excellent EL performance with high luminous efficiency in the green region via solution-processed PHOLEDs has been reported.
关键词： high photoluminescence quantum yields,current efficiency,external quantum efficiency,homoleptic green-emitting meridional iridium (III) complexes,solution-processed green phosphorescence organic light-emitting diodes (PHOLEDs)
更新于2025-09-23 15:19:57
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Gallium nitride micro-light-emitting diode structured light sources for multi-modal optical wireless communications systems
摘要： Gallium nitride-based light-emitting diodes (LEDs) have revolutionized the lighting industry with their efficient generation of blue and green light. While broad-area (square millimetre) devices have become the dominant LED lighting technology, fabricating LEDs into micro-scale pixels (micro-LEDs) yields further advantages for optical wireless communications (OWC), and for the development of smart-lighting applications such as tracking and imaging. The smaller active areas of micro-LEDs result in high current density operation, providing high modulation bandwidths and increased optical power density. Fabricating micro-LEDs in array formats allows device layouts to be tailored for target applications and provides additional degrees of freedom for OWC systems. Temporal and spatial control is crucial to use the full potential of these micro-scale sources, and is achieved by bonding to pitch-matched complementary metal-oxide-semiconductor control electronics. These compact, integrated chips operate as digital-to-light converters, providing optical signals from digital inputs. Applying the devices as projection systems allows structured light patterns to be used for tracking and self-location, while simultaneously providing space-division multiple access communication links. The high-speed nature of micro-LED array devices, combined with spatial and temporal control, allows many modes of operation for OWC providing complex functionality with chip-scale devices.
关键词： Gallium nitride,structured light,light-emitting diodes,optical wireless communications
更新于2025-09-23 15:19:57
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Growth, pigment content, antioxidant activity, and phytoene desaturase gene expression in Caulerpa lentillifera grown under different combinations of blue and red light-emitting diodes
摘要： Light-emitting diodes (LEDs) have been developed as light sources for indoor algae cultivation. In this study, we determined the effects of blue and red light ratios on weight gain, pigment content, antioxidant activity, and phytoene desaturase (PDS) gene expression in Caulerpa lentillifera. Caulerpa lentillifera was grown under six LED light treatments: white (W), red (R, 660 nm, 100%), blue (B, 447 nm, 100%), 1B1R (50% blue + 50% red), 1B2R (33.3% blue + 66.7% red), and 1B5R (16.7% blue + 83.3% red). Our results showed that red light improved the weight gain percentage of C. lentillifera, whereas red light with a low proportion of blue light (1B5R, 16.7%; blue + 83.3% red) led to a significantly higher weight gain percentage and photosynthetic pigment (Chl a + Chl b) content than the other LED light treatments. Increasing the proportion of blue light negatively affected weight gain and the photosynthetic pigment contents. However, blue LED light induced significantly higher transcription of the PDS gene, which coincided with increased β-carotene accumulation and antioxidant activity in C. lentillifera. These results indicated that the ratio of blue to red light is important for the indoor cultivation of C. lentillifera, and 100 μmol photons m?2 s?1 of 1B5R LED light with a 12/12 h light-dark photoperiod resulted in good growth and development.
关键词： Red and blue light ratio,Chlorophyta,Phytoene desaturase,Light-emitting diodes,Caulerpa lentillifera
更新于2025-09-23 15:19:57
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Light extraction from quantum dot light emitting diodes by multiscale nanostructures
摘要： Improving the light extraction efficiency by introducing optical–functional structures outside of quantum dot light emitting diodes (QLED) for further enhancing the external quantum efficiency (EQE) is essential for its application in display and lighting industrialization. Although the efficiency of QLED has been optimized by controlling of the synthesis of the quantum dots, the low outcoupling efficiency is indeed unresolved because of total internal reflections, waveguides and metal surface absorptions within the device. Here, we are utilizing multiscale nanostructures attaching to the outer surface of the glass substrate to extract the trapped light from the emitting layers of QLED. The result indicates that both the EQE and luminance are improved from 12.29% to 17.94% and 122400 cd m-2 to 178700 cd m-2, respectively. The maximum EQE and current efficiency improve to 21.3% and 88.3 cd A?1, respectively, which are the best performance among reported green QLED with light outcoupling nanostructures. The improved performance is ascribed to eliminate total internal reflection by multiscale nanostructures attached to the outer surface of the QLED. Additionally, the simulation result of Finite-difference time domain (FDTD) also demonstrates the light trapping effect is reduced by the multiscale nanostructures. The design of the novel light outcoupling nanostructure for further improving the efficiency of QLED can promote its application in display and lighting industrializations.
关键词： quantum dot light emitting diodes,multiscale nanostructures,light extraction efficiency,external quantum efficiency,display and lighting industrialization
更新于2025-09-23 15:19:57
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Enhanced Optical Output of Near-Ultraviolet Light-Emitting Diodes by a Monolayer of Nanospheres
摘要： The optical output of near-ultraviolet (NUV) light-emitting diodes (LEDs) was improved by including a monolayer of hexagonal close-packed polystyrene (PS) nanospheres. PS nanospheres with different sizes were deposited on the indium tin oxide layer of the NUV LEDs. The electroluminescence results showed that the light extraction efficiency of the NUV LEDs was increased by the inclusion of PS nanospheres, and the maximum optical output enhancement was obtained when the size of the nanospheres was close to the light wavelength. The largest enhancement of the optical output of 1.27-fold was obtained at an injection current of 100 mA. The enhanced optical output was attributed to part of the incident light beyond the critical angle being extracted when the exit surface of the NUV LEDs had a PS nanosphere monolayer. This method may serve as a low-cost and effective approach to raise the efficiency of NUV LEDs.
关键词： polystyrene nanospheres,optical output enhancement,near-ultraviolet,light-emitting diodes,light extraction efficiency
更新于2025-09-23 15:19:57
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Polarization-engineered AlGaN last quantum barrier for efficient deep-ultraviolet light-emitting diodes
摘要： The AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) has been identified as a prospective mercury-free UV source. However, the observation of severe electron overflow and low hole injection efficiency in the conventional DUV LED deteriorates the device performance, attributing to the downward band bending as a result of the strong polarization-induced electric fields between the last quantum barrier (LQB) and the electron blocking layer (EBL). In this study, a composition-graded AlGaN layer with linearly increasing of Al composition from 0.5 to 0.65 is proposed to act as the LQB, replacing the conventional flat LQB to reduce the effective barrier height for hole injection while improving the electron blocking ability. Hence, a considerable enhancement of the output power can be obtained. Moreover, further investigations show that the thickness of graded LQB determine the band bending in the LQB and thus significantly suppress the electron leakage, eventually leading to a boosted output power. The thorough investigation on the LQB could pave the way towards the realization of efficient DUV LEDs of the future.
关键词： electron blocking layer,ultraviolet light-emitting diodes,light output power,polarization field,graded last quantum barrier
更新于2025-09-23 15:19:57
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Light Extraction Efficiency Optimization of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
摘要： Using finite-difference time-domain method, the light extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) is investigated. Simulation results show that compared to flat sapphire substrate, the nano-patterned sapphire substrate (NPSS) expands the extraction angles of top surface and sidewalls. As a result, the LEE of transverse-magnetic (TM) polarized light is improved significantly. Roughening on the backside of n-AlGaN surface significantly enhances the LEE of top surface of thin-film flip-chip DUV LEDs. However, the LEE of sidewalls of thin-film flip-chip DUV LEDs is greatly weakened. For bare DUV LED, the LEE of flip-chip LED on NPSS is estimated to be about 15%, which is around 50% higher than that of thin-film flip-chip DUV LED with roughening on the backside of n-AlGaN surface.
关键词： AlGaN,nano-patterned sapphire substrate,light-emitting diodes,deep-ultraviolet,light extraction efficiency
更新于2025-09-23 15:19:57
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Visible light communication with efficient far-red/near-infrared polymer light-emitting diodes
摘要： Visible light communication (VLC) is a wireless technology that relies on optical intensity modulation and is potentially a game changer for internet-of-things (IoT) connectivity. However, VLC is hindered by the low penetration depth of visible light in non-transparent media. One solution is to extend operation into the “nearly (in)visible” near-infrared (NIR, 700–1000 nm) region, thus also enabling VLC in photonic bio-applications, considering the biological tissue NIR semitransparency, while conveniently retaining vestigial red emission to help check the link operativity by simple eye inspection. Here, we report new far-red/NIR organic light-emitting diodes (OLEDs) with a 650–800 nm emission range and external quantum efficiencies among the highest reported in this spectral range (>2.7%, with maximum radiance and luminance of 3.5 mW/cm2 and 260 cd/m2, respectively). With these OLEDs, we then demonstrate a “real-time” VLC setup achieving a data rate of 2.2 Mb/s, which satisfies the requirements for IoT and biosensing applications. These are the highest rates ever reported for an online unequalised VLC link based on solution-processed OLEDs.
关键词： Visible light communication,IoT,VLC,near-infrared,NIR,organic light-emitting diodes,internet-of-things,biosensing,OLEDs
更新于2025-09-23 15:19:57
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Perdeuterated conjugated polymers for ultralowa??frequency magnetic resonance of OLEDs
摘要： Formation of excitons in OLEDs is spin dependent and can be controlled by electron-paramagnetic resonance, affecting device resistance and electroluminescence yield. We explore electrically detected magnetic resonance in the regime of very low magnetic fields (<1mT). A pronounced feature emerges at zero field in addition to the conventional spin-? Zeeman resonance for which the Larmor frequency matches that of the incident radiation. By comparing a conventional π-conjugated polymer as the active material to a perdeuterated analogue, we demonstrate the interplay between zero-field feature and local hyperfine fields. The zero-field peak results from a quasistatic magnetic-field effect of the RF radiation for periods comparable to the carrier-pair lifetime. Zeeman resonances are resolved down to 3.2MHz, approximately twice the Larmor frequency of an electron in Earth’s field. However, since reducing hyperfine fields sharpens the Zeeman peak at the cost of an increased zero-field peak, we suggest that this result constitutes a fundamental low-field limit of magnetic resonance in carrier-pair-based systems. OLEDs offer an alternative solid-state platform to investigate the radical-pair mechanism of magnetic-field effects in photochemical reactions, allowing models of biological magnetoreception to be explored by measuring spin decoherence directly in the time domain.
关键词： Deuteration,Magnetic resonance,Isotopes,Conjugated Polymers,Organic light-emitting diodes
更新于2025-09-23 15:19:57
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High voltage vacuum-processed perovskite solar cells with organic semiconducting interlayers
摘要： In perovskite solar cells, the choice of appropriate transport layers and electrodes is of great importance to guarantee efficient charge transport and collection, minimizing recombination losses. The possibility to sequentially process multiple layers by vacuum methods offers a tool to explore the effects of different materials and their combinations on the performance of optoelectronic devices. In this work, the effect of introducing interlayers and altering the electrode work function has been evaluated in fully vacuum-deposited perovskite solar cells. We compared the performance of solar cells employing common electron buffer layers such as bathocuproine (BCP), with other injection materials used in organic light-emitting diodes, such as lithium quinolate (Liq), as well as their combination. Additionally, high voltage solar cells were obtained using low work function metal electrodes, although with compromised stability. Solar cells with enhanced photovoltage and stability under continuous operation were obtained using BCP and BCP/Liq interlayers, resulting in an efficiency of approximately 19%, which is remarkable for simple methylammonium lead iodide absorbers.
关键词： stability,perovskite solar cells,bathocuproine,interlayers,electron buffer layers,photovoltage,vacuum-deposited,organic light-emitting diodes,lithium quinolate
更新于2025-09-23 15:19:57