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Organic Electropolymerized Multilayers for Light-Emitting Diodes and Displays
摘要： In electrochemistry, the carbazole generally coupled to dimer but not polymer. This work has reported that organic electropolymerzation (OEP) of 4,4',4"-Tri(N-carbazolyl)triphenylamine (TCTA) would form high crosslinked carbazole polymer by its high activity/reversibility and a synchronous viscosity control. It has significantly improved the OEP film quality of both holes transporting and electroluminescent layers in organic light emitting diodes. As a result, the conductivity and power efficiency of the organic light emitting diodes with TCTA are eight and four times of that without TCTA. A prototype display device with 1.7 inch monochrome passive matrix of 58 ppi under driving chip is successfully fabricated with accurate pixel size and uniform electroluminescence, which makes the big potential of organic electropolymerzation in the electroluminescent application.
关键词： TCTA,Polymerization,Electrochemistry,Carbazole,Organic Light emitting diodes
更新于2025-09-19 17:13:59
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Impact of pixel surface topography onto thin-film encapsulated top-emitting organic light-emitting diodes performances
摘要： Two di?erent designs of top-emitting green OLEDs (Organic Light-Emitting Diodes) have been studied. The ?rst one presents a planar OLED architecture. The second one presents an OLED having a topographic surface, so as to simulate a pixel partitioning of a display using an electrically insulating, 200 nm-thick, resist. It has been observed that the topography has a large impact on OLED performances. Studying devices using an ALD (Atomic Layer Deposition)-deposited Al2O3 barrier ?lm shows that topographic OLEDs have a lower stability under storage in 65 °C/85% RH conditions compared to planar ones, with a di?erence in ageing models between the two devices. As the ALD deposition technology has a high conformity, which implies that ALD-deposited Al2O3 barrier ?lms should be as good on topographic devices as on planar ones, we inferred that the topographic OLED Achilles’ heel lies rather in the OLED structure rather than in the Al2O3 encapsulation itself. Thus, topographic and planar unencapsulated OLEDs (without Al2O3) were studied: interestingly, it has been observed that planar OLEDs can live several weeks, while topographic OLEDs show a very short shelf lifetime (in laboratory atmosphere, at 21 °C/50% RH), of only a couple of hours. It will be shown that the topographic OLED surface tends to reduce the thickness of the PVD (Physical vapour Deposition)-deposited layers in the OLED, as this is expected for a non-conformal deposition PVD technique, on tapered angle regions of the resist (pixel edges). While this thickness variation would not be critical for thick electrodes, as for instance for bottom-emitting devices made on glass substrates, this thickness reduction turns out to be a critical point for the ultrathin, 15 nm, silver cathode, used as semi-transparent electrode in this top-emitting architecture and will therefore be discussed in the framework of using OLED top-emitting architectures in (micro)display technology.
关键词： Dark spots,Physical vapour deposition,Atomic layer deposition,Organic light-emitting diodes,Topography,Degradation
更新于2025-09-19 17:13:59
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Improving the Performance and Stability of Perovskite Light-Emitting Diodes by a Polymeric Nanothick Interlayer-Assisted Grain Control Process
摘要： CsPbBr3 is a promising light-emitting material due to its wet solution processability, high photoluminescence quantum yield (PLQY), narrow color spectrum, and cost-effectiveness. Despite such advantages, the morphological defects, unsatisfactory carrier injection, and stability issues retard its widespread applications in light-emitting devices (LEDs). In this work, we demonstrated a facile and cost-effective method to improve the morphology, efficiency, and stability of the CsPbBr3 emissive layer using a dual polymeric encapsulation governed by an interface-assisted grain control process (IAGCP). An eco-friendly low-cost hydrophilic polymer poly(vinylpyrrolidone) (PVP) was blended into the CsPbBr3 precursor solution, which endows the prepared film with a better surface coverage with a smoothened surface. Furthermore, the poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/emissive layer interface further promotes the film quality and the performance of the derived LED. It is mainly attributed to three major consequences: (i) reduced grain size of the emissive layer, which facilitates charge recombination, (ii) reduced current leakage due to the enhanced electron-blocking effect, and (iii) improved color purity and air stability owing to better defect passivation. As a result, the optimized composite emissive film can retain the luminescence properties even on exposure to ambient conditions for 80 days and ～62% of its initial PL intensity can be preserved after 30 days of storage without any encapsulation.
关键词： efficiency,light-emitting diodes,polymeric nanothick interlayer,grain control process,CsPbBr3,stability
更新于2025-09-19 17:13:59
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Enhanced Emission of Deep Ultraviolet Light-Emitting Diodes Through Using Work Function Tunable Cu Nanowires as Top Transparent Electrode
摘要： Deep ultraviolet light-emitting diodes (DUV LEDs) (< 280 nm) have been important light sources for broad applications in, e.g., sterilization, purification, high-density storage and etc. However, the lack of excellent transparent electrodes in DUV region remains a challenging issue. Here, we demonstrate an architectural engineering scheme to flexibly tune the work function of Cu@shell nanowires (NWs) as top transparent electrodes in DUV LEDs. By fast encapsulation of shell metals on Cu NWs and shift of electron binding energy, the electronic work function could be widely tailored down to 4.37 eV and up to 5.73 eV. It is revealed that the high work function of Cu@Ni and Cu@Pt NWs could overcome the interfacial barrier to p-AlGaN and achieve direct ohmic contact with high transparency (91%) in 200 ~ 400 nm. Completely transparent DUV LED chips are fabricated and successfully lighted with sharp top emission (wall-plug efficiency reaches 3 %) under a turn-on voltage of 6.4 V. This architectural strategy is of importance in providing highly transparent ohmic electrodes for optoelectronic devices in broad wavelength regions.
关键词： copper nanowires,transparent electrodes,light-emitting diodes,Deep ultraviolet,work function
更新于2025-09-19 17:13:59
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Highly efficient blue organic light-emitting diodes based on carbene-metal-amides
摘要： Carbene-metal-amides are soluble and thermally stable materials which have recently emerged as emitters in high-performance organic light-emitting diodes. Here we synthesise carbene-metal-amide photoemitters with CF3-substituted ligands to show sky-blue to deep-blue photoluminescence from charge-transfer excited states. We demonstrate that the emission colour can be adjusted from blue to yellow and observe that the relative energies of charge transfer and locally excited triplet states influence the performance of the deep-blue emission. High thermal stability and insensitivity to aggregation-induced luminescence quenching allow us to fabricate organic light-emitting diodes in both host-free and host-guest architectures. We report blue devices with a peak external quantum efficiency of 17.3% in a host-free emitting layer and 20.9% in a polar host. Our findings inform the molecular design of the next generation of stable blue carbene-metal-amide emitters.
关键词： charge-transfer excited states,photoluminescence,carbene-metal-amides,organic light-emitting diodes,external quantum efficiency
更新于2025-09-19 17:13:59
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High-efficiency perovskite nanocrystal light-emitting diodes <i>via</i> decorating NiO <sub/>x</sub> on the nanocrystal surface
摘要： Nickel oxides exhibit a great potential as hole transport layers for the fabrication of efficient perovskite light-emitting diodes (LEDs) due to their high carrier mobility and good energy band matching with perovskite nanocrystals. In this work, nickel oxides were directly decorated on the CsPbBr3 nanocrystal surface through adsorption and a sequential oxidation treatment. The resulting sample shows a high photoluminescence quantum-yield of 82%. The LED using CsPbBr3 nanocrystals with nickel oxides achieves a high external quantum efficiency (EQE) of up to 16.8% with a low turn-on voltage of 2.8 V, which is much superior to that of the counterpart LED based on pristine CsPbBr3 nanocrystals (EQE = 0.7%, turn-on voltage = 5.6 V). The excellent performance of the nickel oxide decorated CsPbBr3 nanocrystal device could be attributed to the better energy level matching between the decorated nanocrystals and the transport layers of the device and more balanced charge carrier injection. Furthermore, the operational lifetime of the nickel oxide decorated CsPbBr3 nanocrystal device is 40 times longer than that of the pristine CsPbBr3 nanocrystal device.
关键词： perovskite nanocrystals,photoluminescence quantum-yield,light-emitting diodes,external quantum efficiency,nickel oxides
更新于2025-09-19 17:13:59
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Highly Elastic and >200% Reversibly Stretchable Downa??Conversion White Lighta??Emitting Diodes Based on Quantum Dot Gel Emitters
摘要： Combining the characteristics of different materials offers exciting new opportunities for advanced applications in various fields. Herein, white light-emitting diodes (WLEDs) with >200% reversible stretchability are fabricated using six-color quantum dots (QDs) gel emitters. Stable aqueous-phase alloy core/shell QDs with high quantum yield are obtained via ligand exchange using a ternary solvent system. Transparent and highly stretchable gels with large pores are created by binary-solvent-based gelation at low temperatures. Importantly, the QDs and the gel originate from the same two solvents, which make the QDs highly compatible with the gelation process. Consequently, QDs of six different colors are incorporated into the gel without any property degradation. The excellent optical properties of the QDs in the liquid phase (e.g., 17% higher photoluminescence (PL) intensity) are retained in the gel phase. The QD gel (QDG) exhibits elastic deformation up to 200%, with uniform PL over the entire gel. A down-conversion WLED built using the QDG emitter produces cool white light with a color temperature of 6100 K, a color rendering index of 94, and a luminous efficacy of 72 lm W?1. In addition, the performance of the QDG-based WLED remains unchanged even after more than 1000 bending/stretching cycles.
关键词： white light emitting diodes,gels,mechanical reliability,form factors,quantum dots
更新于2025-09-19 17:13:59
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Bright and Color-Stable Blue-Light-Emitting Diodes based on Three-Dimensional Perovskite Polycrystalline Films via Morphology and Interface Engineering
摘要： Substantial progress has been achieved in red and green perovskite light-emitting diodes (PeLEDs). However, blue PeLEDs are still inferior in light-emitting efficiency and luminance compared with their green and red counterparts. Herein efficient blue PeLEDs simultaneously achieving high luminance and high color stability are fabricated based on the polycrystalline perovskites with a 3D Rb?Cs alloyed scaffold. The synergistic manipulation of an isopropanol antisolvent treatment and the PEDOT:PSS/blue perovskite interface modification with RbCl effectively improve the photoluminescence properties of the resultant blue polycrystalline 3D perovskite films and the final electroluminescence performance of the blue PeLEDs. The optimized blue PeLEDs show a maximum external quantum efficiency of 1.66% with an emission peak at 484 nm and a full width at half-maximum of 18 nm as well as CIE coordinates of (0.08, 0.21). Moreover, the optimized blue PeLEDs not only show superior color stability under various luminances but also achieve high luminances. The obtained maximum luminance of 9243 cd m?2 is one of the highest values among the efficient and color-stable blue PeLEDs.
关键词： blue PeLEDs,perovskite light-emitting diodes,Rb?Cs alloyed scaffold,color stability,high luminance
更新于2025-09-19 17:13:59
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Two-dimensional Ruddlesdena??Popper layered perovskite for light-emitting diodes
摘要： Solution-processed metal halide perovskite light-emitting diodes (PeLEDs) have attracted extensive attention due to the great potential application in energy-efficient lighting and displays. Two-dimensional Ruddlesden–Popper (2DRP) layered perovskites exhibit high photoluminescence quantum efficiency, improved film morphology, and enhanced operational stability over their three-dimensional counterparts, making them attractive for high-performance PeLEDs. In addition, 2DRP perovskite materials with a tunable exciton binding energy are suitable for preparing PeLEDs with color-tunability. In this perspective, we first introduce the merits of the 2DRP layered perovskites in terms of their structural characteristics. The progress in 2DRP PeLEDs is then reviewed. The challenges and new opportunities of the PeLEDs are finally discussed. We hope to open up new perspectives for rational designs of the 2DRP perovskite materials for PeLEDs with unprecedented efficiency and stability.
关键词： operational stability,film morphology,photoluminescence quantum efficiency,Two-dimensional Ruddlesden–Popper layered perovskite,color-tunability,light-emitting diodes
更新于2025-09-19 17:13:59
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Influence of Silicon-Doping in n-AlGaN Layer on the Optical and Electrical Performance of Deep Ultraviolet Light-Emitting Diodes
摘要： The influence of two different methods of silicon doping in AlGaN layer, that is, modulation-doping (MD) and delta-doping (DD), on the optical and electrical performance of deep ultraviolet light-emitting diodes (DUV-LEDs) has been investigated. Both the photoluminescence and electroluminescence intensities in the Si-DD structure are stronger than those obtained by the Si-MD method, while the forward voltage and reverse leakage current are slightly smaller in the DD structure than that in the MD structure. Compared with the MD structure, the DD structure shows higher capacitance-voltage characteristics. This study suggests that the DD method can improve the optical and electrical performance of DUV-LEDs.
关键词： bias voltage,n-AlGaN layer,ultraviolet light-emitting diodes,capacitance,Si-doping,current
更新于2025-09-19 17:13:59