Junqiao Ding

High‐Efficiency Single Emissive Layer White Organic Light‐Emitting Diodes Based on Solution‐Processed Dendritic Host and New Orange‐Emitting Iridium Complex

An extremely high-efficiency solution-processed white organic light-emitting diode (WOLED) is successfully developed by simultaneously using an ideal dendritic host material and a novel efficient orange phosphorescent iridium complex. The optimized device exhibits forward-viewing efficiencies of 70.6 cd A(-1) , 26.0%, and 47.6 lm W(-1) at a luminance of 100 cd m(-2) , respectively, promising the low-cost solution-processed WOLEDs a bright future as the next generation of illumination sources.

Self-host blue-emitting iridium dendrimer with carbazole dendrons: nondoped phosphorescent organic light-emitting diodes.

A blue-emitting iridium dendrimer, namely B-G2, has been successfully designed and synthesized with a secondgeneration oligocarbazole as the dendron, which is covalently attached to the emissive tris[2-(2,4-difluorophenyl)-pyridyl]iridium(III) core through a nonconjugated link to form an efficient self-host system in one dendrimer. Unlike small molecular phosphors and other phosphorescent dendrimers, B-G2 shows a continuous enhancement in the device efficiency with increasing doping concentration. When using neat B-G2 as the emitting layer, the nondoped device is achieved without loss in efficiency, thus giving a state-of-art EQE as high as 15.3% (31.3 cdA1, 28.9 lmW1) along with CIE coordinates of (0.16, 0.29).

Solution-Processable Carbazole-Based Conjugated Dendritic Hosts for Power-Efficient Blue-Electrophosphorescent Devices

A novel class of hosts suitable for solution processing has been developed based on a conjugated dendritic scaffold. By increasing the dendron generation, the highest occupied molecular orbital (HOMO) energy level can be tuned to facilitate hole injection, while the triplet energy remains at a high level, sufficient to host high-energy-triplet emitters. A power-efficient blue-electrophosphorescent device based on H2 is presented.

Design of star-shaped molecular architectures based on carbazole and phosphine oxide moieties: towards amorphous bipolar hosts with high triplet energy for efficient blue electrophosphorescent devices

With a carbazole moiety as the electron donor and a phosphine-oxide moiety as the electron acceptor, two novel star-shaped bipolar hosts, 4,4′,4″-tri(N-carbazolyl)triphenylphosphine oxide (TCTP) and 3,6-bis(diphenylphosphoryl)-9-(4′-(diphenylphosphoryl)phenyl)carbazole (TPCz), have been designed and synthesized. Their topology structure differences are that the phosphine-oxide moiety is located in the molecular centre and the periphery for TCTP and TPCz, respectively. The star-shaped architecture imparts them with high decomposition temperatures (Td: 497 °C for TCTP and 506 °C for TPCz) and results in the formation of a stable amorphous glassy state (Tg: 163 °C for TCTP and 143 °C for TPCz), while the phosphine oxide linkage ensures the disrupted conjugation and the high triplet energy (>3.0 eV). In addition, both TCTP and TPCz possess a bipolar transporting capability. However, TCTP mostly transports holes and TPCz primarily conducts electrons. On the basis of appropriate device configurations, high performance blue electrophosphorescent devices with comparable efficiency (35.0–36.4 cd A−1, 15.9–16.7%) have been realized using TCTP and TPCz as the host for the blue phosphor, respectively. Compared with the unipolar host, 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA, 15.9 cd A−1, 7.8%), the efficiency is improved by more than two-fold. As far as the obtained state-of-the-art performance is concerned, we think that these novel materials should provide an avenue for the design of amorphous bipolar hosts with high triplet energy used for blue PhOLEDs on a star-shaped scaffold.

A Novel, Bipolar Polymeric Host for Highly Efficient Blue Electrophosphorescence: a Non‐Conjugated Poly(aryl ether) Containing Triphenylphosphine Oxide Units in the Electron‐Transporting Main Chain and Carbazole Units in Hole‐Transporting Side Chains

A novel, bipolar polymeric host based on a poly(aryl ether) containing phosphine oxide units in the electron-transporting main chain and carbazole units in the hole-transporting side chains is designed and synthesized for blue electrophosphorescence. This polymeric host possesses a bipolar character and a high E(T) of 2.96 eV. The efficiency of blue-emitting PhPLEDs based on this polymeric host doped with Flrpic reaches 23.3 cd A(-1) (EQE = 10.8%).

Highly efficient single-emitting-layer white organic light-emitting diodes with reduced efficiency roll-off

By codoping blue and orange phosphorescent dyes into a single host material, a highly efficient white organic light-emitting diode (WOLED) with Commission Internationale de L’Eclairage coordinates of (0.38, 0.43) at 12 V is demonstrated. Remarkably, this WOLED achieves reduced current efficiency roll-off, which slightly decreases from its maximum value of 37.3–31.0 cd/A at 1000 cd/m2. The device operational mechanism is subsequently investigated in order to unveil the origin of the high performance.

Solution-Processed Phosphorescent Organic Light-Emitting Diodes with Ultralow Driving Voltage and Very High Power Efficiency

To realize power efficient solution-processed phosphorescent organic light-emitting diodes (s-PhOLEDs), the corresponding high driving voltage issue should be well solved. To solve it, efforts have been devoted to the exploitation of novel host or interfacial materials. However, the issues of charge trapping of phosphor and/or charge injection barrier are still serious, largely restraining the power efficiency (PE) levels. Herein, with the utilization of an exciplex-forming couple 4, 4′, 4″ -tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA) and 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB), the efficient charge injection and transporting, barrier-free hole-electron recombination for the formation of the interfacial exciplex, and elimination of charge traps of phosphors in the emissive layer are realized simultaneously, resulting in a turn-on voltage of 2.36 V, a record high PE of 97.2 lm W−1, as well as extremely low driving voltage of 2.60 V at 100 cd m−2, 3.03 V at 1000 cd m−2 and 4.08 V at 10000 cd m−2. This report is the first time that the PE performance of s-PhOLED approaches 100 lm W−1 high level, even superior to the corresponding state-of-the-art performance of the same color vacuum-deposited PhOLED (v-PhOLED) counterpart. We anticipate this report opens a new avenue for achieving power efficient monochromatic and white s-PhOLEDs with simple structures.

A high-performance tandem white organic light-emitting diode combining highly effective white-units and their interconnection layer

By utilizing 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline:Li/MoO3 as an effective charge generation layer (CGL), we extend our recently demonstrated single-emitting-layer white organic light-emitting diode (WOLED) to realize an extremely high-efficiency tandem WOLED. This stacked device achieves maximum forward viewing current efficiency of 110.9 cd/A and external quantum efficiency of 43.3% at 1 μA/cm2 and emits stable white light with Commission Internationale de L’Eclairage coordinates of (0.34, 0.41) at 16 V. It is noted that the combination of effective single units and CGL is key prerequisite for realizing high-performance tandem WOLEDs.

Detection of explosives with porous xerogel film from conjugated carbazole-based dendrimers

The carbazole-based conjugated dendrimer H2-BCz with tert-butyl surface groups shows selective gelation behavior in a good solvent and anti-solvent mixture. The sol–gel conversion of H2-BCz can be observed on heating and cooling. The H2-BCz xerogel films show three-dimensional porous networks with the nanofibers (layered structures with a period of 1.38 nm) entangling and intersecting with each other. The π–π interactions between the aryl units may be the driving force for the formation of one-dimensional H2-BCz fibers during the gelation process. Due to the electron-donating property of the H2-BCz molecule and the porosity of the fibrous film, the xerogel films can be used as efficient fluorescence quenching based chemsensors for the detection of nitroaromatic explosives, such as 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT). The quenching efficiency was as high as 77% and 91% when exposed to the vapor of TNT and DNT, respectively.

Starburst 4,4′,4′′-tris(carbazol-9-yl)-triphenylamine-based deep-blue fluorescent emitters with tunable oligophenyl length for solution-processed undoped organic light-emitting diodes

On the basis of a well-known hole transporting material, namely 4,4′,4′′-tris(carbazol-9-yl)-triphenylamine (TCTA), a series of star-shaped deep-blue fluorescent emitters (2P-TCTA, 3P-TCTA, 4P-TCTA and 5P-TCTA) have been successfully developed via a simple extension of the oligophenyl chain between two N atoms. When the number of phenyl rings increases, it is found that both the absorption and emission for these TCTA-based starbursts are red-shifted and finally become saturated for 5P-TCTA consisting of a pentaphenyl bridge. Interestingly, on going from 2P-TCTA to 5P-TCTA, the film photoluminescence quantum yield is gradually enhanced from 11.4% to 35.5%. The same trend is also observed for their corresponding solution-processed undoped OLEDs. As a consequence, 5P-TCTA shows the best device performance, revealing a maximum luminescence of 7300 cd m−2, and a peak luminous efficiency of 2.48 cd A−1 (2.15 lm W−1; 2.30%) together with CIE coordinates of (0.15, 0.09).