Yibin Jiang

Construction of efficient blue AIE emitters with triphenylamine and TPE moieties for non-doped OLEDs

In this paper, by merging the hole-dominated triphenylamine (TPA) and tetraphenylethene (TPE) moieties together with different linkage positions, four derivatives of 1,2-bis[4′-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene (2TPATPE) were successfully synthesized with confirmed structures, and their thermal, optical and electronic properties were fully investigated. Thanks to the introduction of the meta-linkage mode on the TPE core, their π-conjugation length could be effectively restricted to ensure blue emission. The non-doped OLEDs based on these four emitters exhibit blue emissions from 443–466 nm, largely blue-shifted with respect to the green emission of 2TPATPE (514 nm). Meanwhile, good electroluminescence efficiencies with Lmax, ηC,max, and ηP,max of up to 8160 cd m−2, 3.79 cd A−1, and 2.94 Im W−1 respectively, have also been obtained, further validating our rational design of blue AIE fluorophores.

Rational Design of Aggregation-Induced Emission Luminogen with Weak Electron Donor–Acceptor Interaction to Achieve Highly Efficient Undoped Bilayer OLEDs

In this work, two tailored luminogens (TPE-NB and TPE-PNPB) consisting of tetraphenylethene (TPE), diphenylamino, and dimesitylboryl as a π-conjugated linkage, electron donor, and electron acceptor, respectively, are synthesized and characterized. Their thermal stabilities, photophysical properties, solvachromism, fluorescence decays, electronic structures, electrochemical behaviors, and electroluminescence (EL) properties are investigated systematically, and the impacts of electron donor-acceptor (D-A) interaction on optoelectronic properties are discussed. Due to the presence of a TPE unit, both luminogens show aggregation-induced emission, but strong D-A interaction causes a decrease in emission efficiency and red-shifts in photoluminescence and EL emissions. The luminogen, TPE-PNPB, with a weak D-A interaction fluoresces strongly in solid film with a high fluorescence quantum yield of 94%. The trilayer OLED [ITO/NPB (60 nm)/TPE-PNPB (20 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] utilizing TPE-PNPB as a light emitter shows a peak luminance of 49 993 cd m(-2) and high EL efficiencies up to 15.7 cd A(-1), 12.9 lm W(-1), and 5.12%. The bilayer OLED [ITO/TPE-PNPB (80 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] adopting TPE-PNPB as a light emitter and hole transporter simultaneously affords even better EL efficiencies of 16.2 cd A(-1), 14.4 lm W(-1), and 5.35% in ambient air, revealing that TPE-PNPB is an eximious p-type light emitter.

Efficient vacuum-free-processed quantum dot light-emitting diodes with printable liquid metal cathodes

Colloidal quantum dot light-emitting diodes (QLEDs) are recognized as promising candidates for next generation displays. QLEDs can be fabricated by low-cost solution processing except for the metal electrodes, which, in general, are deposited by costly vacuum evaporation. To be fully compatible with the low-cost solution process, we herein demonstrate vacuum-free and solvent-free fabrication of electrodes using a printable liquid metal. With eutectic gallium-indium (EGaIn) based liquid metal cathodes, vacuum-free-processed QLEDs are demonstrated with superior external quantum efficiencies of 11.51%, 12.85% and 5.03% for red, green and blue devices, respectively, which are about 2-, 1.5- and 1.1-fold higher than those of the devices with thermally evaporated Al cathodes. The improved performance is attributable to the reduction of electron injection by the native oxide of EGaIn, which serves as an electron-blocking layer for the devices and thus improves the balance of carrier injection. Also, the T50 half-lifetime of the vacuum-free-processed QLEDs is about 2-fold longer than that of the devices with Al cathodes. Our results demonstrate that EGaIn-based solvent-free liquid metals are promising printable electrodes for realizing efficient, low-cost and vacuum-free-processed QLEDs. The elimination of vacuum and high-temperature processes significantly reduces the production cost and paves the way for industrial roll-to-roll manufacturing of large area displays.

Synthesis, Structure, Photoluminescence, and Electroluminescence of Siloles that Contain Planar Fluorescent Chromophores

Herein, a new series of siloles that were 2,5-substituted with planar fluorescent chromophores (PFCs), including fluorene, fluoranthene, naphthalene, pyrene, and anthracene, were synthesized and characterized. These compounds showed weak emission in the solution state, owing to active intramolecular rotation (IMR), but the synergistic effect from electronic coupling between the PFC and the silole ring compensated for the emission quenching by the IMR process to some extent, thereby affording higher emission efficiencies than those of 2,3,4,5-tetraphenylsiloles in solution. These new siloles showed enhanced emission efficiencies in the aggregated state. The electroluminescence (EL) color and efficiency of new siloles were sensitive towards the PFC. Siloles containing naphthalene moieties showed green EL emission, whilst those containing anthracene moieties showed orange EL emission. The siloles containing pyrene moieties exhibited yellow EL emission at 546 nm, with a peak luminance of 49000 cd cm(-2) and a high current efficiency of 9.1 cd A(-1).

Overcoming the Limitations of Sputtered Nickel Oxide for High‐Efficiency and Large‐Area Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) are one of the promising photovoltaic technologies for solar electricity generation. NiOx is an inorganic p‐type semiconductor widely used to address the stability issue of PSCs. Although high efficiency is obtained for the devices employing NiOx as the hole transport layer, the fabrication methods have yet to be demonstrated for industrially relevant manufacturing of large‐area and high‐performance devices. Here, it is shown that these requirements can be satisfied by using the magnetron sputtering, which is well established in the industry. The limitations of low fill factor and short‐circuit current commonly observed in sputtered NiOx‐derived PSCs can be overcome through magnesium doping and low oxygen partial pressure deposition. The fabricated PSCs show a high power conversion efficiency of up to 18.5%, along with negligible hysteresis, improved ambient stability, and high reproducibility. In addition, good uniformity is also demonstrated over an area of 100 cm2. The simple and well‐established approach constitutes a reliable and scale method paving the way for the commercialization of PSCs.

Selective wetting/dewetting for controllable patterning of liquid metal electrodes for all-printed device application

Liquid metals based on eutectic gallium–indium (EGaIn) alloys are promising printable electrode materials for various printed devices such as light-emitting diodes or solar cells. To achieve a controllable and fine patterning of the EGaIn electrodes, herein, a facile bottom-up, additive technique has been developed by manipulating wetting/dewetting of the substrate. The substrate is first dewetted by coating a hydrophobic layer; then, to selectively dewet the substrate, the coated hydrophobic layer is patterned by laser ablation. EGaIn, which is painted onto the substrate, can only adhere to the wetting regions and thus can perfectly copy the patterns of the wetting regions. Via this method, high-resolution EGaIn patterns with a line width smaller than 100 μm can be obtained. Using the patterned EGaIn electrodes, all-printed quantum dot light-emitting diodes were successfully demonstrated. The proposed method offers a feasible route for fast patterning of EGaIn and thus allows for inexpensive, rapid fabrication of various devices without the need of costly vacuum processing.

Grid Optimization of Large-Area OLED Lighting Panel Electrodes

Luminance loss resulting from potential drop on the transparent indium tin oxide (ITO) electrode due to its relatively high resistivity is one of the most essential issues in the design of large-area organic light-emitting diode (OLED) lighting panels. One solution is to pattern metal grid with low sheet resistance on the ITO electrode. However, the shape, height, and width of the metal grid element have a great influence on the final luminance uniformity of the device. In this paper, a method is proposed to optimize these parameters in order to get the best luminance uniformity for large-area OLED lighting panels. The method takes two grid geometry parameters-height and width-into account and predicts the highest relative luminance by finite element method simulations under different operating voltages.