Chuluo Yang

Bio: Chuluo Yang is an academic researcher from Huazhong University of Science and Technology. The author has contributed to research in topics: Carbazole & Phosphorescent organic light-emitting diode. The author has an hindex of 7, co-authored 7 publications receiving 418 citations. Previous affiliations of Chuluo Yang include Wuhan University.

Simple Phenanthroimidazole/Carbazole Hybrid Bipolar Host Materials for Highly Efficient Green and Yellow Phosphorescent Organic Light-Emitting Diodes

Abstract: By conjugating carbazole moiety to the different positions of the rigid skeleton 1,2-diphenyl-1H-phenanthro[9,10-d]imidazole, a series of hybrid bipolar phosphorescent hosts was synthesized, and their photophysical properties were investigated. The introduction of a rigid phenanthroimidazole moiety greatly improves their morphological stability, with high decomposition temperatures (Td) and high glass transition temperatures (Tg) in the range of 394–417 and 113–243 °C, respectively. The highly efficient green and orange phosphorescent organic light-emitting diodes (PhOLEDs) have been achieved by employing these compounds as the phosphorescent hosts. For the device of ITO/MoO3 (10 nm)/NPB (80 nm)/TCTA (5 nm)/mPhBINCP:9 wt % Ir(ppy)3 (20 nm)/TmPyPB (45 nm)/LiF (1 nm)/Al (100 nm), a maximum luminous efficiency (ηc,max) of 77.6 cd/A, maximum power efficiency (ηp,max) of 80.3 lm/W, and maximum external quantum efficiency (ηEQE,max) of 21% were obtained. Furthermore, these hosts are also applicable for the oran...

Controllably tunable phenanthroimidazole–carbazole hybrid bipolar host materials for efficient green electrophosphorescent devices

Abstract: A series of phenanthroimidazole–carbazole (1 : 2) hybrids as bipolar host materials have been designed and synthesized through facile typical Ullmann reactions. These compounds with rigid configurations exhibit excellent thermal and morphological stabilities with high glass transition temperatures (Tg) (143–282 °C). Their photoelectronic properties, energy levels, charge transport mobility, and film morphologies can be controllably tuned through judicious engineering of the linkage modes between the two carbazole groups and the 2,5-diphenyl-1,3,4-phenanthroimidazole (para and meta). The promising physical properties of these new compounds make them suitable for use as hosts doped with Ir-based phosphor for realizing highly efficient phosphorescent organic light emitting diodes (PhOLEDs). A green device hosted by compound PhBIDmpCP shows a maximum current efficiency of 74.3 cd A−1 and a maximum power efficiency of 74.4 lm W−1 (corresponding EQEmax = 20.2%).

Novel Deep Blue OLED Emitters with 1,3,5-Tri(anthracen-10-yl)benzene-Centered Starburst Oligofluorenes

Abstract: A series of starburst materials (T1−T3) bearing a 1,3,5-tri(anthracen-10-yl)benze-ne core (T0) and three oligofluorenes arms have been synthesized and characterized. Single-crystal diffraction analysis has shown that the core of these starburst materials possess a propeller twist topology, which made the starburst materials exhibit good film-forming capabilities and display deep blue emission both in solution and in the thin solid film. The compounds (T1−T3) possess high glass transition temperatures (Tg’s) at 107, 109, and 110 °C, and high decomposition temperatures (Td’s) at 438, 440, and 434 °C, respectively. In addition, the double-layered devices fabricated with the three materials as the emitter show a stable deep-blue emission and the device performance increases with arm length at some extent. The double-layered device based on T2 has a maximum brightness of over 3400 cd/m2 and a maximum current efficiency of 1.80 cd/A with CIE coordinates of (0.149, 0.098), which is among the best of the deep-blu...

Benzimidazole–carbazole-based bipolar hosts for high efficiency blue and white electrophosphorescence applications

Abstract: A series of novel bipolar blue phosphorescent host materials mBICP, mBINCP and mBIPhCP have been designed and synthesized, which comprehensively outperform the widely used phosphorescent host, 1,3-di(9H-carbazol-9-yl)benzene (mCP). The thermal, photophysical and electrochemical properties of these host materials were finely tuned through linking different carbazole moieties to the benzimidazole. mBICP (Tg = 84 °C) and mBIPhCP (Tg = 103 °C) exhibit high morphological stabilities in comparison with mCP. Theoretical calculations show that the HOMO/LUMO orbitals of these materials are mainly dispersed on the electron donating and electron accepting groups, respectively. A blue PhOLED device fabricated using mBICP as the host exhibits a maximum external quantum efficiency (ηEQE,max) of 18.7% and a maximum power efficiency (ηP,max) of 33.6 lm W−1. Interestingly, the external quantum efficiencies (ηEQE) are still as high as 17.1% at a high luminance of 1000 cd m−2. Furthermore, the two-color, all-phosphor and single-emitting-layer white device hosted by mBICP achieved a maximum external quantum efficiency (ηEQE,max) of 20.5% corresponding to a maximum power efficiency (ηP,max) of 53.3 lm W−1.

Simple Bipolar Hosts with High Glass Transition Temperatures Based on 1,8-Disubstituted Carbazole for Efficient Blue and Green Electrophosphorescent Devices with “Ideal” Turn-on Voltage

Abstract: Two hybrids based on 1,8-disubstituted carbazole, 1,8-OXDCz and 1,8-mBICz, have been designed and synthesized through a facile process. The incorporation of oxadiazole or N-phenylbenzimidazole moieties at the 1,8-positions of carbazole greatly improves its morphological stability, giving glass transition temperatures (T(g)) as high as 138 and 154 °C, respectively. Blue phosphorescent organic light-emitting devices (PhOLEDs) with 1,8-mBICz exhibit almost the same performance as a similarly structured device based on the mCP host, and green PhOLEDs employing the new host material 1,8-OXDCz exhibit an ideal turn-on voltage (2.5 V at 1.58 cd m(-2)), a maximum current efficiency (η(c,max)) of 73.9 cd A(-1), and a power efficiency (η(p,max)) of 89.7 lm W(-1). These results are among the best performances of [Ir(ppy)(3)]-based devices with simple device configurations.

Blue fluorescent emitters: design tactics and applications in organic light-emitting diodes

Abstract: Organic light-emitting diodes (OLEDs) are competitive candidates for the next generation flat-panel displays and solid state lighting sources. Efficient blue-emitting materials have been one of the most important prerequisites to kick off the commercialization of OLEDs. This tutorial review focuses on the design of blue fluorescent emitters and their applications in OLEDs. At first, some typical blue fluorescent materials as dopants are briefly introduced. Then nondoped blue emitters of hydrocarbon compounds are presented. Finally, the nondoped blue emitters endowed with hole-, electron- and bipolar-transporting abilities are comprehensively reviewed. The key issues on suppressing close-packing, achieving pure blue chromaticity, improving thermal and morphological stabilities, manipulating charge transporting abilities, simplifying device structures and the applications in panchromatic OLEDs are discussed.

Functionalization of phosphorescent emitters and their host materials by main-group elements for phosphorescent organic light-emitting devices.

Abstract: Phosphorescent organic light-emitting devices (OLEDs) have attracted increased attention from both academic and industrial communities due to their potential practical application in high-resolution full-color displays and energy-saving solid-state lightings. The performance of phosphorescent OLEDs is mainly limited by the phosphorescent transition metal complexes (such as iridium(III), platinum(II), gold(III), ruthenium(II), copper(I) and osmium(II) complexes, etc.) which can play a crucial role in furnishing efficient energy transfer, balanced charge injection/transporting character and high quantum efficiency in the devices. It has been shown that functionalized main-group element (such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur and fluorine, etc.) moieties can be incorporated into phosphorescent emitters and their host materials to tune their triplet energies, frontier molecular orbital energies, charge injection/transporting behavior, photophysical properties and thermal stability and hence bring about highly efficient phosphorescent OLEDs. So, in this review, the recent advances in the phosphorescent emitters and their host materials functionalized with various main-group moieties will be introduced from the point of view of their structure-property relationship. The main emphasis lies on the important role played by the main-group element groups in addressing the key issues of both phosphorescent emitters and their host materials to fulfill high-performance phosphorescent OLEDs.

Recent advances of the emitters for high performance deep-blue organic light-emitting diodes

Abstract: Blue organic light-emitting diodes (OLEDs) can play a critical role in the field of organic electroluminescence (EL). As the most important applications of OLEDs, both new generation full-color flat-panel displays and future energy-saving solid-state lighting sources require blue color EL to fulfill their functions properly. However, considerable challenges still exist in searching for highly efficient, color stable, and long-lifespan materials and devices that emit blue color, especially in the development of deep-blue emitters, which are indispensable for high-quality displays and lighting sources. Encouragingly, great progress has been made in the area of deep-blue OLEDs in recent years with continuous efforts made by scientists, who are responsible for the significant achievements in the field of OLEDs. Hence, in this review, the crucial tactics employed to obtain high performance deep-blue emitters are presented, including polymers, dendrimers, small organic molecules, delayed fluorescent systems, and phosphorescent emitters. Moreover, the future perspectives and ongoing challenges of this research frontier are also highlighted.

Yellow/orange emissive heavy-metal complexes as phosphors in monochromatic and white organic light-emitting devices

Abstract: Owing to the electron spin-orbit coupling (SOC) and fast intersystem crossing (ISC), heavy-metal complexes (such as iridium(III), platinum(II) and osmium(II) complexes, etc.) are phosphorescent emitters at room temperature. Since 1998, heavy-metal complexes as phosphors have received considerable academic and industrial attention in the field of organic light-emitting diodes (OLEDs), because they can harvest both the singlet (25%) and triplet (75%) excitons for emission during the electro-generated processes. Among all the visible colors (blue, green, yellow, orange and red), the yellow/orange heavy-metal complexes play an important role for realizing full-color OLEDs as well as high-efficiency white OLEDs, and thus the development of highly efficient yellow/orange heavy-metal complexes is a pressing concern. In this article, we will review the progress on yellow/orange heavy-metal complexes as phosphors in OLEDs. The general principles and useful tactics for designing the yellow/orange heavy-metal complexes will be systematically summarized. The structure-property relationship and electrophosphorescence performance of the yellow/orange heavy-metal complexes in monochromatic phosphorescent OLEDs (PhOLEDs) and white OLEDs (WOLEDs) will be comprehensively surveyed and discussed.

Efficient Deep Blue Electroluminescence with an External Quantum Efficiency of 6.8% and CIEy < 0.08 Based on a Phenanthroimidazole–Sulfone Hybrid Donor–Acceptor Molecule

Abstract: Tremendous efforts have been devoted to develop efficient deep blue organic light-emitting diodes (OLEDs) materials with CIEy < 0.10 (Commission International de L’Eclairage (CIE)) and match the National Television System Committee (NTSC) standard blue CIE (x, y) coordinates of (0.14, 0.08) for display applications. However, deep blue fluorescent materials with an external quantum efficiency (EQE) over 5% are still rare. Herein, we report a phenanthroimidazole–sulfone hybrid donor–acceptor (D–A) molecule with efficient deep blue emission. D–A structure molecular design has been proven to be an effective strategy to obtain high electroluminescence (EL) efficiency. In general, charge transfer (CT) exciton formed between donor and acceptor is a weak coulomb bonded hole–electron pair and is favorable for the spin flip that can turn triplet excitons into singlet ones. However, the photoluminescence quantum yield (PLQY) of CT exciton is usually very low. On the other hand, a locally excited (LE) state normally ...