Honglong Ning

Extremely high-efficiency and ultrasimplified hybrid white organic light-emitting diodes exploiting double multifunctional blue emitting layers

Numerous hybrid white organic light-emitting diodes (WOLEDs) have recently been developed. However, their efficiency is not comparable to that of their best all-phosphorescent WOLED counterparts, and the structures are usually complicated, restricting their further development. Herein, a novel concept is used to achieve a hybrid WOLED, whose crucial feature is the exploitation of double multifunctional blue emitting layers. The three-organic-layer WOLED exhibits a total efficiency of 89.3 and 65.1 lm W–1 at 100 and 1000 cd m–2, respectively, making it the most efficient hybrid WOLED reported in the literature so far. Significantly, the efficiencies of hybrid WOLEDs have, for the first time, been demonstrated to be comparable to those of the best all-phosphorescent WOLEDs. In addition, the device exhibits the lowest voltages among hybrid WOLEDs (i.e., 2.4, 2.7 and 3.1 V for 1, 100 and 1000 cd m–2, respectively). Such remarkable performance achieved from such an ultrasimplified structure opens a new path toward low-cost commercialization.

Precipitation in Cu–Ni–Si–Zn alloy for lead frame

Abstract The aging of Cu–Ni–Si–Zn alloy for lead frame is investigated. The results showed that the peak of hardening effect occurs after aging for about 1 h and the electrical conductivity increases continuously with aging times. The hardness of the alloy reached a peak at 430–460 °C for 2 h and electrical conductivity reached a peak at 500–550 °C and continuously decreased afterwards. The cold rolling prior to the aging treatment was used to increase the precipitation rate. The precipitates responsible for the age-hardening effect are disc-shaped δ-Ni 2 Si, which has an orthorhombic structure.

Efficient hybrid white organic light-emitting diodes with extremely long lifetime: the effect of n-type interlayer

The effect of n-type interlayer in hybrid white organic light-emitting diodes (WOLEDs) has been systematically investigated by using various n-type materials. A new finding, that the triplet energy rather than electron mobility or hole-blocking ability of interlayer plays a more positive role in the performance of hybrid WOLEDs, is demonstrated. Based on the new finding, a more efficient n-type interlayer bis[2-(2-hydroxyphenyl)-pyridine] beryllium has been employed to realize a high-performance hybrid WOLED. The resulting device (without n-doping technology) exhibits low voltages (i.e., 2.8 V for 1 cd/m2, 3.9 V for 100 cd/m2) and low efficiency roll-off (i.e., 11.5 cd/A at 100 cd/m2 and 11.2 cd/A at 1000 cd/m2). At the display-relevant luminance of 100 cd/m2, a total power efficiency of 16.0 lm/W, a color rendering index of 73 and an extremely long lifetime of 12596265 h are obtained. Such superior results not only comprehensively indicate that the n-type materials are effective interlayers to develop high-performance hybrid WOLEDs but also demonstrate a significant step towards real commercialization in WOLEDs.

Joining of sapphire and hot pressed Al2O3 using Ag70.5Cu27.5Ti2 brazing filler metal

Abstract Sapphire and hot-pressed 99% Al2O3 ceramic were joined using Ag70.5Cu27.5Ti2 bracing filler metal in a vacuum electric furnace. The interface reaction between Ag70.5Cu27.5Ti2 alloy and sapphire, hot-pressed Al2O3 ceramic during brazing is reported. The joining strength and the airtight of the specimen are influenced by the surface condition of Al2O3 ceramic and the factor of active brazing condition.

Preoxidation of the Cu layer in direct bonding technology

Abstract Between the metal melting point and the eutectic temperature of the metal–oxygen, direct bonded copper (DBC) depends on the eutectic composition to join the copper and ceramic. The key of this technology is to import the oxygen to the bonding surface. In this paper, we do some research on the preoxidation law of the copper layer in direct bonding technology, so we can optimize the rang of preoxidation temperature and time. After we investigate the phase diagram of copper–oxygen, by the “conservation of mass” and “level principle”, we find there are some relationship between the preoxidation condition and the bonding process, and we offer a experiential formula to help control the bonding process. Finally, we also analyze the interface reaction production between the Cu layer and alumina ceramic, and discuss some possible reasons.

High-Performance Doping-Free Hybrid White OLEDs Based on Blue Aggregation-Induced Emission Luminogens

Doping-free white organic light-emitting diodes (DF-WOLEDs) have aroused research interest because of their simple properties. However, to achieve doping-free hybrid WOLEDs (DFH-WOLEDs), avoiding aggregation-caused quenching is challenging. Herein, blue luminogens with aggregation-induced emission (AIE) characteristics, for the first time, have been demonstrated to develop DFH-WOLEDs. Unlike previous DFH-WOLEDs, both thin (<1 nm) and thick (>10 nm) AIE luminogen (AIEgen) can be used for devices, enhancing the flexibility. Two-color devices show (i) pure-white emission, (ii) high CRI (85), and (iii) high efficiency. Particularly, 19.0 lm W1- is the highest for pure-white DF-WOLEDs, while 35.0 lm W1- is the best for two-color hybrid WOLEDs with CRI ≥ 80. A three-color DFH-WOLED shows broad color-correlated temperature span (2301-11628 K), (i) the first sunlight-like OLED (2500-8000 K) operating at low voltages, (ii) the broadest span among sunlight-like OLED, and (iii) possesses comparable efficiency with the best doping counterpart. Another three-color DFH-WOLED exhibits CRI > 90 at ≥3000 cd m-2, (i) the first DF-WOLED with CRI ≥ 90 at high luminances, and (ii) the CRI (92.8) is not only the highest among AIE-based WOLEDs but also the highest among DF-WOLEDs. Such findings may unlock an alternative concept to develop DFH-WOLEDs.

A host–guest system comprising high guest concentration to achieve simplified and high-performance hybrid white organic light-emitting diodes

Single-emitting-layer (single-EML) hybrid white organic light-emitting diodes (WOLEDs) have attracted a great deal of attention due to their simplified structures. However, the guest concentration is usually too low, which is quite difficult to control and reproduce in the coevaporation process. Herein, for the first time, N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine has been used as both the host and the blue emitter in single-EML WOLEDs. By dint of this multifunctional material, the concentration is found to be as high as 1.5%. This device exhibits a maximum total efficiency of 65.3 lm W−1, indicating a significant step towards the real commercialization. Besides, low voltages (i.e., the turn-on voltage is 2.4 V and 3.45 V at 1000 cd m−2) and a color rendering index (CRI) of 77 are obtained for this two-color WOLED. Unlike the working mechanisms in previous single-EML hybrid WOLEDs with low guest concentrations, devices comprising high concentrations exhibit more sophisticated engineering, in which the device smartly allows the utilization of both the fluorescence from the host itself, and the complementary phosphorescence from the guest by incomplete Forster energy transfer, Dexter energy transfer as well as direct exciton formation on the guest. Moreover, we have incorporated this unique host–guest system into a dual-EML hybrid WOLED. Maximum efficiencies of 17.2 lm W−1 and 10.2 lm W−1 at 1000 cd m−2 (3.85 V) with an ultrahigh CRI of 93 are achieved, providing a new opportunity to accomplish the simplified structure/low voltage/high efficiency/ultrahigh CRI trade-off.

High-mobility thin film transistors with neodymium-substituted indium oxide active layer

Thin-film transistors (TFTs) with neodymium-substituted indium oxide (InNdO) channel layer were demonstrated. The structural properties of the InNdO films as a function of annealing temperature have been analyzed using X-ray diffraction and transmission electron microscopy. The InNdO thin films showed polycrystalline nature when annealed at 450 °C with a lattice parameter (cubic cell) of 10.255 A, which is larger than the cubic In2O3 film (10.117 A). The high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy showed that no Nd2O3 clusters were found in the InNdO film, implying that Nd was incorporated into the In2O3 lattice. The InNdO TFTs annealed at 450 °C exhibited more excellent electrical properties with a high mobility of 20.4 cm2 V−1 s−1 and better electric bias stability compared to those annealed at 300 °C, which was attributed to the reduction of the scattering centers and/or charge traps due to the decrease of the |Nd3d5/254f4O2p−1⟩ electron configuration.

Solution-processed indium-zinc-oxide thin-film transistors based on anodized aluminum oxide gate insulator modified with zirconium oxide

Solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs) based on anodized aluminum oxide gate insulator modified with a zirconium oxide (ZrOx) interlayer were fabricated. By introduction of the ZrOx interlayer, the IZO-TFTs exhibited improved performance with a higher mobility of 7.8 cm2 V−1 s−1, a lower Vth of 4.6 V and a lower SS of 0.21 V dec−1 compared to those without the ZrOx interlayer. Comprehensive studies showed that the Al element easily diffused into the IZO film and formed AlOx clusters which acted as defects to deteriorate TFT performance; and after modification with a ZrOx interlayer, the diffusion of Al was suppressed and the Zr diffusing effect almost could be ignored. These results suggested that the introduction of an interlayer with less diffusing effect as well as an effect of blocking the elements from the gate insulator diffusing into the channel layer could be an effective way to improve the electrical performance for solution-processed oxide TFTs.

Method for Fabricating Amorphous Indium-Zinc-Oxide Thin-Film Transistors With Copper Source and Drain Electrodes

We revealed a novel method to fabricate amorphous indium-zinc-oxide (a-IZO) thin-film transistors (TFTs) with inverted staggered back-channel-etch structure and copper (Cu) source/drain (S/D) electrodes. In particular, a gray-tone mask was used to define the S/D electrodes and active layer. The a-IZO layer acted not only as the active layer but also as the adhesive layer of Cu electrodes due to the good adhesion between Cu and a-IZO films. The presented TFTs exhibited a high saturated mobility of 12.2 cm2/Vs, a threshold voltage of -0.4 V, and a low subthreshold swing of 0.22 V/decade. The good electrical performance and reliability were attributed to the good contact property between Cu electrodes and a-IZO layer and very little Cu atoms diffusing into the channel layer.