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A negative polaron resistant p-type host for extended lifetime in deep blue phosphorescent organic light-emitting diodes
摘要： A novel mixed host employing a negative polaron stabilizing p-type host was developed to extend the device lifetime of blue phosphorescent organic light-emitting diodes (PhOLEDs). Instead of a conventional p-type host with only a hole transport unit, a p-type host with a negative polaron resistant unit in addition to the hole transport unit was used in the mixed host consisting of a p-type host and an n-type host. The p-type host had benzonitrile as a negative polaron resistant unit which stabilized the molecule under negative polarons. The use of the p-type host with the benzonitrile unit almost doubled the device lifetime of the blue PhOLEDs due to the improved negative polaron stability of the hosts. Therefore, the p-type host with the weak electron accepting benzonitrile unit can play the role of a lifetime extending p-type host to replace a conventional p-type host.
关键词： p-type host,device lifetime,negative polaron,benzonitrile,blue phosphorescent organic light-emitting diodes
更新于2025-09-23 15:19:57
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Interactive Colora??Changing Electronic Skin Based on Flexible and Piezoelectrically Tunable Quantum Dots Lighta??Emitting Diodes
摘要： Inspired by animals in nature, such as chameleons, frogs, and cephalopods, the remarkable capability of changing one’s skin color has drawn considerable interests due to its wide applications in camouflage, warning methods, and visual communications. Today, research on electronic skins (e-skins), imitating biological skin by quantifying external stimuli, to mimic this unique color-changing function has been achieved based on the integration of a matrix of displays and sensors; however, integrated systems possess bulky and complicated fabrication processes. Here, the first attempt to demonstrate a single user-interactive e-skin device with color-changing response upon applied external strain is made, while using a cost-effective and space-saving method, which promises to open new possibilities for the development of next-generation e-skins with visual response.
关键词： user-interactive devices,flexible light emitting diodes,electronic skin
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： The 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 (< 1 mT). A pronounced feature emerges at zero field in addition to the conventional spin-1=2 Zeeman resonance for which the Larmor frequency matches that of the incident radiation. By comparing a conventional p-conjugated polymer as the active material to a perdeuterated analogue, we demonstrate the interplay between the 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 3.2 MHz, approximately twice the Larmor frequency of an electron in Earth(cid:3)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 may constitute 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 tested by measuring spin decoherence directly in the time domain by pulsed experiments.
关键词： conjugated polymers,deuteration,magnetic resonance,isotopes,organic light-emitting diodes
更新于2025-09-23 15:19:57
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Crosslinkinga??Induced White Light Emission of Poly(Hydroxyurethane) Microspheres for White LEDs
摘要： Nonconjugated luminescent polymers with white light emission are promising for a wide range of applications in display and lighting devices, but their preparation remains a big challenge. Herein, a white-light-emitting nonconjugated poly(hydroxyurethane) microsphere (PHUM) synthesized from the crosslinking reaction of trimethylolpropane tri(cyclic carbonate) ether and 1,6-hexanediamine in chloroform is reported. The resultant PHUMs possess uniform sizes ranging from 12.6 to 21.5 μm. It is proposed that a high crosslinking degree and various hydrogen-bonding strengths induce the formation of carbamate clusters with different sizes and broad distributions, which result in a broad emission spectrum. The cluster-size distribution effect leads to multiple n–π* transitions from various carbamate clusters via through-space conjugation of carbamates, realizing white light emission. In addition, the application of PHUMs as single phosphor combined with a 365 nm UV chip is also demonstrated, with which a white-light-emitting diode with a high color rendering index of up to 95 is obtained. This work confirms that crosslinking can induce multiple emissions, which provides a new clusteroluminescence and polymerization-induced emission system for tunable luminescence emission.
关键词： through-space conjugation,light-emitting diodes,poly(hydroxyurethane) microspheres,clusteroluminescence,H-bonding
更新于2025-09-23 15:19:57
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Multiscale Simulation of Photoluminescence Quenching in Phosphorescent OLED Materials
摘要： A multiscale simulation protocol to treat triplet–triplet annihilation (TTA) in phosphorescent organic light-emitting diodes (PhOLEDs), in which microscopic parameters are computed with ab initio electronic structure methods, is presented. Virtual photoluminescence experiments are performed on a prototypical PhOLED emission material consisting of 4,4?,4?-tris(N-carbazolyl)triphenylamine and fac-tris(2-phenylpyridine)iridium. The obtained TTA quenching rate is comparable to experimental results in the low-intensity limit.
关键词： multiscale modeling,organic light-emitting diodes,exciton quenching,triplet–triplet annihilation
更新于2025-09-23 15:19:57
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Direct conjugation with a zero length linker of fullerene C <sub/>70</sub> to ZnO quantum dots for multicolor light-emitting diodes
摘要： Environmentally friendly metal oxide quantum dots (QDs) nanostructures has become attractive alternative materials for replacing QDs containing toxic elements of Cd and Pb. Although many attempts have been proposed for optoelectronic applications of hybrid metal oxide QDs with tailored opto-electronic properties, the fabrication of heterogeneous QD-fullerene hybrids as an emissive material has been little studied for optoelectronic devices. Herein, we report the preparation of ZnO-fullerene C70 (ZnO-C70) QDs by facile chemical reaction with zero length linker and demonstrate whitish light-emitting diodes by fullerene induced multicolor emission from ZnO-C70 QDs heterostructure. The electroluminescence (EL) is attributed to three new emission features in the visible region that originates from the electron transitions from three split lowest unoccupied molecular orbital levels of C70 molecules to the valence band of ZnO QDs. Compared with photoluminescence, the EL emissions were red-shifted by 50 - 130 meV due to the interaction between ZnO-C70 QDs in solid state. Energy levels of C70 were also suitably aligned to those of ZnO QDs with lower electron transfer barrier of 0.22 eV, which offers an advantageous route for electron transport. Consequently, the environmentally friendly ZnO-C70 QDs with extraordinary properties promise great potential for use as novel encapsulating materials in the field of opto-electronic applications adopting QDs.
关键词： Fullerene C70,Light emitting diodes,ZnO-fullerene C70 heterostructure,C60,Quantum dots,0D-0D heterostructures
更新于2025-09-23 15:19:57
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Solution-processed blue quantum-dot light-emitting diodes based on double hole transport layers: Charge injection balance, solvent erosion control and performance improvement
摘要： Solution processed quantum-dot based light emitting diodes (QLEDs) usually suffer from the issues of imbalanced carrier injection (especially for blue QLEDs) and solvent erosion, which prevents these devices from reaching high performance. Here we report a simple and effective method of promoting hole injection and mitigating solvent erosion simultaneously for fabricating high-performance blue QLEDs. Poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(p-butylphenyl))-diphenylamine)] (TFB)/Lithium bis(trifluoromethanesulfonimide) (Li-TFSI)-doped poly(9-vinlycarbazole) (PVK) bi-layers with smooth surfaces/interfaces, prepared via a solution-process by utilizing 1,4-dioxane as the solvent for PVK, were used as hole transport layers (HTLs) for improving the performance of blue QLEDs. The TFB/Li-doped PVK based QLED records 5829 cd/m2 of maximum brightness and 5.37% of peak EQE, which represents 1.1-fold increase in brightness and ~11.5-fold increase in EQE as compared with the devices based on TFB-only HTLs. The enhanced performance for these TFB/Li-doped PVK based QLEDs can be ascribed to more efficient hole injection offered by Li-doped bilayer HTLs with smooth surfaces/interfaces and stepwise energy level alignment. The CIE 1931 color coordinates (0.15, 0.03) for these TFB/Li-doped PVK based QLEDs are close to the National Television System Committee (NTSC) standard blue CIE coordinates, showing promise for use in next-generation full-color displays. This work provides a facile solution method of fabricating TFB/Li-doped PVK bi-layers with smooth surfaces/interfaces and proves the superiority of these TFB/Li-doped PVK bi-layered HTLs in hole transport and injection for high-performance blue QLEDs.
关键词： double hole transport layers,blue quantum-dot light-emitting diodes,charge injection；Lithium salt doped hole transport layer,solvent erosion,solution processability
更新于2025-09-23 15:19:57
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Realizing 22.3% EQE and 7-Fold Lifetime Enhancement in QLED: via Blending Polymer TFB and Cross-linkable Small Molecule for Solvent-Resistant Hole Transport Layer
摘要： Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt(4,4'-(N-(4-butylphenyl))] (TFB) has been widely used as a hole transport layer (HTL) material in cadmium-based quantum dots light-emitting diodes (QLEDs) due to its high hole mobility. However, as the highest occupied molecular orbital (HOMO) energy level of TFB is -5.4 eV, the hole injection from TFB to quantum dots (QDs) layer is higher than 1.5 eV. Such high oxidation potential at the QD/HTL interface may seriously degrade the device lifetime. In addition, TFB is not resistant to most solvents, which limits its application in inkjet-printed QLEDs display. In this study, blended HTL consisting of TFB and cross-linkable small molecular 4,4 ′ -bis(3-vinyl-9H-carbazol-9-yl)1,1 ′ -biphenyl (CBP-V) was introduced into red QLEDs, because of the deep HOMO energy level of CBP-V (-6.2 eV). Compared with the TFB only devices, the external quantum efficiency (EQE) of devices with blended HTL improved from 15.9 % to 22.3 % without the increase of turn-on voltage for spin-coating fabricated device. Furthermore, the blended HTL prolonged the T90 and T70 lifetime from 5.4 h and 31.1 h to 39.4 h and 148.9 h, respectively. These enhancements in lifetime are attributed to the low hole-injection barrier at HTL/QD interface and high thermal stability of blended HTL after crosslinking. Moreover, the crosslinked blended HTL showed excellent solvent resistance after cross-linking and the EQE of the inkjet-printed red QLEDs reached 16.9 %.
关键词： charge balance,quantum dots light-emitting diodes,blended HTL,solvent resistance,inkjet printing
更新于2025-09-23 15:19:57
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Efficient quantum-dot light-emitting diodes using ZnSa??AgInS <sub/>2</sub> solid-solution quantum dots in combination with organic charge-transport materials
摘要： Colloidal quantum dots (QDs), which exhibit highly saturated color emission, are expected to be used as emitting materials in wide-color-gamut displays. However, the development of low-toxicity alternatives is necessary because QDs with high color purity and highly efficient emission contain toxic materials such as Cd and Pb. In this study, QD light-emitting diodes (QD-LEDs) with ZnS–AgInS2 solid-solution nanoparticles [(AgIn)xZn2(1?x)S2, ZAIS] as low-toxicity QDs were fabricated and their electroluminescence properties were investigated. The ZAIS QDs exhibited red photoluminescence, with a peak wavelength of ca. 700 nm. Because the charge-injection barrier of ZAIS QDs without a wide-bandgap shell is relatively low, the QD-LEDs with red ZAIS QDs in combination with organic charge-transport materials induce electron injection from an organic electron-transport layer. These QD-LEDs exhibit an external quantum efficiency of 2.2%, a turn-on voltage of 2.4 V, and red emission with chromaticity coordinates (0.66, 0.33).
关键词： quantum dots,electroluminescence,low-toxicity,light-emitting diodes,ZnS–AgInS2
更新于2025-09-23 15:19:57
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Phase control of quasi-2D perovskites and improved light-emitting performance by excess organic cations and nanoparticle intercalation
摘要： The optoelectronic properties of quasi-two-dimensional organic–inorganic hybrid perovskites can be tuned by controlling the formation of Ruddlesden–Popper type phases, which enables diverse device applications such as photovoltaics and light-emitting diodes (LEDs). Herein, the influence of excess organic cations on the phase formation of (PEA)2MAn?1PbnBr3n+1 is systematically investigated with various mixing ratios to discover the phase distribution beneficial for light-emitting diodes. It is found that PEA cations exceeding Pb ions in molar ratio are required to produce small-n phases in the films with a strong photoluminescence, while excess MA cations enable the formation of more large-n phases. Low electrical conductivity inherent to the properties of quasi-2D perovskites is further lowered by the introduction of excess organic cations. This is overcome by the intercalation of zinc oxide (ZnO) nanoparticles (NPs) into the blocking layers composed of PEA cations. Importantly, these metal oxide NPs also modulate the phase distribution, enabling the realization of bright green quasi-2D perovskites with a better stability and a maximum luminance of nearly 60 000 cd m?2, which is the highest brightness compared to the so far reported quasi-2D perovskite LEDs incorporating organic cations.
关键词： phase control,excess organic cations,nanoparticle intercalation,light-emitting diodes,quasi-2D perovskites
更新于2025-09-19 17:15:36