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1.
Due to the difficulty in achieving high efficiency and high color purity simultaneously, blue emission is the limiting factor for the performance and stability of OLEDs. Since 2003, we have been working on organic light‐emitting diodes (OLEDs), especially on blue light. After a series of molecular designs, novel strategies have been proposed from different aspects. At first, highly efficient deep blue emission could be achieved through molecular design with highly twisted structure to suppress fluorescence quenching and redshift. Deep blue emitters with high efficiency in solid state, a twisted structure with aggregation induced emission (AIE) characteristics was incorporated to inhibit molecular aggregation, and triplet‐triplet fusion (TTF) and hybridized localized charge transfer (HLCT) were adopted to increase the ratio of triplet exciton used. Secondly, a highly efficient blue OLED could be achieved through improving charge transport. New electron transport materials (ETMs) with wide band gap were developed to control charge transport balance in devices. Thirdly, a highly efficient deep blue emission could be achieved through a mesoscopic structure of out‐coupling layer. A mesoscopic photonic structured organic thin film was fabricated on the top of metal electrode by self‐aggregation in order to improve the light out‐coupling efficiency. 相似文献
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Prof. Guijiang Zhou Yue He Bing Yao Jingshuang Dang Prof. Wai‐Yeung Wong Prof. Zhiyuan Xie Prof. Xiang Zhao Prof. Lixiang Wang 《化学:亚洲杂志》2010,5(11):2405-2414
By combining the iridium(III) ppy‐type complex (Hppy=2‐phenylpyridine) with a square‐planar platinum(II) unit, some novel phosphorescent oligometallaynes bearing dual metal centers (viz. IrIII and PtII) were developed by combining trans‐[Pt(PBu3)2Cl2] with metalloligands of iridium possessing bifunctional pendant acetylene groups. Photophysical and computational studies indicated that the phosphorescent excited states arising from these oligometallaynes can be ascribed to the triplet emissive IrIII ppy‐type chromophore, owing to the obvious trait (such as the longer phosphorescent lifetime at 77 K) also conferred by the PtII center. So, the two different metal centers show a synergistic effect in governing the photophysical behavior of these heterometallic oligometallaynes. The inherent nature of these amorphous materials renders the fabrication of simple solution‐processed doped phosphorescent organic light‐emitting diodes (PHOLEDs) feasible by effectively blocking the close‐packing of the host molecules. Saliently, such a synergistic effect is also important in affording decent device performance for the solution‐processed PHOLEDs. A maximum brightness of 3 356 cd m?2 (or 2 708 cd m?2), external quantum efficiency of 0.50 % (or 0.67 %), luminance efficiency of 1.59 cd A?1 (or 1.55 cd A?1), and power efficiency of 0.60 Lm W?1 (or 0.55 Lm W?1) for the yellow (or orange) phosphorescent PHOLEDs can be obtained. These results show the great potential of these bimetallic emitters for organic light‐emitting diodes. 相似文献
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Chi‐Ming Che Prof. Dr. Chi‐Chung Kwok Dr. Siu‐Wai Lai Dr. Andreas F. Rausch Dipl.‐Chem. Walter J. Finkenzeller Dr. Nianyong Zhu Dr. Hartmut Yersin Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):233-247
The syntheses, crystal structures, and detailed investigations of the photophysical properties of phosphorescent platinum(II) Schiff base complexes are presented. All of these complexes exhibit intense absorption bands with λmax in the range 417–546 nm, which are assigned to states of metal‐to‐ligand charge‐transfer (1MLCT) 1[Pt(5d)→π*(Schiff base)] character mixed with 1[lone pair(phenoxide)→π*(imine)] charge‐transfer character. The platinum(II) Schiff base complexes are thermally stable, with decomposition temperatures up to 495 °C, and show emission λmax at 541–649 nm in acetonitrile, with emission quantum yields up to 0.27. Measurements of the emission decay times in the temperature range from 130 to 1.5 K give total zero‐field splitting parameters of the emitting triplet state of 14–28 cm?1. High‐performance yellow to red organic light‐emitting devices (OLEDs) using these platinum(II) Schiff base complexes have been fabricated with the best efficiency up to 31 cd A?1 and a device lifetime up to 77 000 h at 500 cd m?2. 相似文献
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Fang‐Chung Chen Shun‐Chi Chang Gufeng He Seungmoon Pyo Yang Yang Masayuki Kurotaki Junji Kido 《Journal of Polymer Science.Polymer Physics》2003,41(21):2681-2690
Energy transfer and triplet exciton confinement in polymer/phosphorescent dopant systems have been investigated. Various combinations of host‐guest systems have been studied, consisting of two host polymers, poly(vinylcarbazole) (PVK) and poly[9,9‐bis(octyl)‐fluorene‐2,7‐diyl] (PF), blended with five different phosphorescent iridium complexes with different triplet energy levels. These combinations of hosts and dopants provide an ideal situation for studying the movement of triplet excitons between the host polymers and dopants. The excitons either can be confined at the dopant sites or can flow to the host polymers, subject to the relative position of the triplet energy levels of the material. For PF, because of its low triplet energy level, the exciton can flow back from the dopants to PF when the dopant has a higher triplet energy and subsequently quench the device efficiency. In contrast, efficient electrophosphorescence has been observed in doped PVK films because of the high triplet energy level of PVK. Better energy transfer from PVK to the dopants, as well as triplet exciton confinement on the dopants, leads to higher device performance than found in PF devices. Efficiencies as high as 16, 8.0, and 2.6 cd/A for green, yellow, and red emissions, respectively, can be achieved when PVK is selected as the host polymer. The results in this study show that the energy transfer and triplet exciton confinement have a pronounced influence on the device performance. In addition, this study also provides material design and selection rules for the efficient phosphorescent polymer light‐emitting diodes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2681–2690, 2003 相似文献
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Jing Huang Runli Tang Tian Zhang Prof. Qianqian Li Prof. Gui Yu Shuyi Xie Prof. Yunqi Liu Dr. Shanghui Ye Prof. Jingui Qin Prof. Zhen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(18):5317-5326
Two aggregation‐induced emission active luminogens (TPE–pTPA and TPE–mTPA) were successfully synthesized. For comparison, another six similar compounds were prepared. Because of the introduced hole‐dominated triphenylamine (TPA), fluorene groups with high luminous efficiency, and unconjugated linkages, the π conjugation length of the obtained luminogens is effectively restricted to ensure their blue emission. The undoped organic light‐emitting diodes based on TPE–pTPA and TPE–mTPA exhibited blue or deep‐blue emissions, low turn‐on voltages (3 V), and high electroluminescence efficiencies with Lmax, ηC,max, and ηP,max values of up to 26 697 cd m?2, 3.37 cd A?1, and 2.40 Lm W?1. 相似文献
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Hua Chen Prof. Dr. Zuo‐Quan Jiang Chun‐Hong Gao Mei‐Feng Xu Shou‐Cheng Dong Lin‐Song Cui Prof. Dr. Shun‐Jun Ji Prof. Dr. Liang‐Sheng Liao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11791-11797
A novel silicon‐based compound, 10‐phenyl‐2′‐(triphenylsilyl)‐10H‐spiro[acridine‐9,9′‐fluorene] (SSTF), with spiro structure has been designed, synthesized, and characterized. Its thermal, electronic absorption, and photoluminescence properties were studied. Its energy levels make it suitable as a host material or exciton‐blocking material in blue phosphorescent organic light‐emitting diodes (PhOLEDs). Accordingly, blue‐emitting devices with iridium(III) bis[(4,6‐difluorophenyl)‐pyridinato‐N,C2′]picolinate (FIrpic) as phosphorescent dopant have been fabricated and show high efficiency with low roll‐off. In particular, 44.0 cd A?1 (41.3 lm W?1) at 100 cd m?2 and 41.9 cd A?1 (32.9 lm W?1) at 1000 cd m?2 were achieved when SSTF was used as host material; 28.1 lm W?1 at 100 cd m?2 and 20.6 lm W?1 at 1000 cd m?2 were achieved when SSTF was used as exciton‐blocking layer. All of the results are superior to those of the reference devices and show the potential applicability and versatility of SSTF in blue PhOLEDs. 相似文献
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Dr. Soo-Byung Ko Dr. Sunwoo Kang Prof. Taekyung Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7767-7773
A high triplet energy host is developed using a silane moiety, 9-(4-(triphenylsilyl)dibenzo[b,d]furan-2-yl)-9H-carbazole (SiDBFCz), is designed through extensive density functional theory (DFT) calculations to obtain appropriate hole and electron injection barriers. The chemical hardness and the charge transport characteristics are comprehensively investigated to realize a bipolar host with high triplet energy over 2.9 eV for deep blue phosphorescent organic light-emitting diodes (PHOLEDs). The synthesized SiDBFCz clearly exhibits the bipolar characteristics especially with emitter molecules doped. An external quantum efficiency over 19 % without any microcavity optimization is achieved thanks to the good charge balance in the SiDBFCz PHOLED. The device lifetime of the SiDBFCz PHOLED is improved more than 1000 %, compared to the unipolar control devices at an initial luminance of 500 cd m−2. The dramatic enhancement of the operational stability of the deep blue PHOLED is also thoroughly investigated in terms of electrochemical stability of host molecules in charged or excited states. The results clearly indicate that the device lifetime is strongly correlated with the bond dissociation energy and the activation energy for the bond dissociation reaction in triplet excited state. 相似文献
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Highly Efficient Near‐Infrared Delayed Fluorescence Organic Light Emitting Diodes Using a Phenanthrene‐Based Charge‐Transfer Compound 下载免费PDF全文
Shipan Wang Xianju Yan Zong Cheng Prof. Dr. Hongyu Zhang Prof. Dr. Yu Liu Prof. Dr. Yue Wang 《Angewandte Chemie (International ed. in English)》2015,54(44):13068-13072
Significant efforts have been made to develop high‐efficiency organic light‐emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) emitters with blue, green, yellow, and orange–red colors. However, efficient TADF materials with colors ranging from red, to deep‐red, to near‐infrared (NIR) have been rarely reported owing to the difficulty in molecular design. Herein, we report the first NIR TADF molecule TPA‐DCPP (TPA=triphenylamine; DCPP=2,3‐dicyanopyrazino phenanthrene) which has a small singlet–triplet splitting (ΔEST) of 0.13 eV. Its nondoped OLED device exhibits a maximum external quantum efficiency (EQE) of 2.1 % with a Commission International de L′Éclairage (CIE) coordinate of (0.70, 0.29). Moreover, an extremely high EQE of nearly 10 % with an emission band at λ=668 nm has been achieved in the doped device, which is comparable to the most‐efficient deep‐red/NIR phosphorescent OLEDs with similar electroluminescent spectra. 相似文献
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Dr. Xinxin Ban Dr. Feng Chen Dr. Jie Pan Dr. Yan Liu Dr. Aiyun Zhu Wei Jiang Yueming Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(14):3090-3102
Highly efficient solution-processable emitters are greatly desired to develop low-cost organic light-emitting diodes (OLEDs). The recently developed thermally activated delayed fluorescence (TADF) materials are promising candidates, but blue TADF materials compatible with the all-solution-process have still not been achieved. Here, a series of TADF materials, named X-4CzCN, are developed by introducing the bulky units through an unconjugated linker, which realizes high molecular weight to enhance the solvent resistance ability without disturbing the blue TADF feature. Meanwhile, the peripheral wrapping groups efficiently inhibit the triplet–triplet and triplet–polaron quenching by isolating the energy-transfer and charge-transporting channels. The photophysical measurements indicate that a small variation in peripheral unit will have a noticeable effect on the luminescence efficiency. The enlarged volume of peripheral units will make the electroluminescent spectra blueshift, while enhancing the energy transfer of exciplex and blocking the energy leakage of electromer can facilitate the exciton utilization. As a result, the fully solution-processed blue OLED achieves a CIE of (0.16, 0.27), a low turn on voltage of 2.9 eV, and a high external quantum efficiency of 20.6 %. As far as we known, this is the first report of all-solution-processed TADF OLEDs with blue emission, which exhibits a high efficiency even comparable to the vacuum-deposited devices. 相似文献
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Ai‐hui Liang Sheng Dong Kai Zhang Xiao Xiao Fei Huang Xu‐Hui Zhu Yong Cao 《Macromolecular rapid communications》2013,34(16):1301-1305
Novel supramolecular phosphorescent polymers (SPPs) are synthesized as a new class of solution‐processable electroluminescent emitters. The formation of these SPPs takes advantage of the efficient non‐bonding assembly between bis(dibenzo‐24‐crown‐8)‐functionalized iridium complex monomer and bis(dibenzylammonium)‐tethered co‐monomer, which is monitored by 1H NMR spectroscopy and viscosity measurements. These SPPs show good film morphology and an intrinsic glass transition with a Tg of 94–116 °C. Noticeably, they are highly photoluminescent in solid state with quantum efficiency up to ca. 78%. The photophysical and electroluminescent properties are strongly dependent on the molecular structures of the iridium complex monomers.
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Hongyu Zhen Wei Xu Wei Yang Qiliang Chen Yunhua Xu Jiaxing Jiang Junbiao Peng Yong Cao 《Macromolecular rapid communications》2006,27(24):2095-2100
Summary: A strategy to generate an efficient white‐light emission has been developed by mixing fluorescence and phosphorescence emission from a single polymer. Fluorene is used as the blue‐emissive component, benzothiadiazole (BT) and the iridium complex [(btp)2Ir(tmd)] are incorporated into a polyfluorene backbone, respectively, as green‐ and red‐emissive chromophores by Suzuki polycondensation. By changing the contents of BT and [(btp)2Ir(tmd)] in the polymer, the electroluminescence spectrum from a single polymer can be adjusted to achieve white‐light emission. A white polymeric light‐emitting diode (WPLED) with a structure of ITO/PEDOT:PSS/PVK/PFIrR1G03/CsF/Al shows a maximum external quantum efficiency of 3.7% and the maximum luminous efficiency of 3.9 cd · A−1 at the current density of 1.6 mA · cm−2 with the CIE coordinates of (0.33, 0.34). The maximum luminance of 4 180 cd · m−2 is achieved at the current density of 268 mA · cm−2 with the CIE coordinates of (0.31, 0.32). The white‐light emissions from such polymers are stable in the white‐light region at all applied voltages, and the electroluminescence efficiencies decline slightly with the increasing current density, thus indicating that the approach of incorporating singlet and triplet species into the polymer backbone is promising for WPLEDs.
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Jiwon Yoon Seong Keun Kim Hyung Jong Kim Dr. Suna Choi Sang Won Jung Hyuna Lee Dr. Jun Yun Kim Dr. Dae-Wi Yoon Dr. Chang Wook Han Dr. Weon-Sik Chae Prof. Jang Hyuk Kwon Dr. Min Ju Cho Prof. Dong Hoon Choi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16383-16391
In this study, two host materials, pCzBzbCz and pCzPybCz , are synthesized to achieve a high efficiency and long lifetime of blue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The molecular design strategy involves the introduction of a pyridine group into the core structure of pCzPybCz as an electron-withdrawing unit, and an electron-donating phenyl group into the structure of pCzBzbCz . These host materials demonstrate good thermal stability and high triplet energy (T1=3.07 eV for pCzBzbCz and 3.06 eV for pCzPybCz ) for the fabrication of blue TADF-OLEDs. In particular, pCzPybCz -based OLED devices demonstrate an external quantum efficiency (EQE) of 22.7 % and an operational lifetime of 24 h (LT90, time to attain 90 % of initial luminance) at an initial luminance of 1000 cd m−2. This superior lifetime could be explained by the C−N bond dissociation energy (BDE) in the host molecular structure. Furthermore, a mixed-host system using the electron-deficient 2,4-bis(dibenzo[b,d]furan-2-yl)-6-phenyl-1,3,5-triazine (DDBFT) is proposed to inhibit the formation of the anion state of our host materials. In short, the device operational lifetime is further improved by applying DDBFT. The carbazole-based asymmetric host molecule containing a pyridine core realizes a high-efficiency blue TADF-OLED showing a positive effect on the operating lifetime, and can provide useful strategies for designing new host materials. 相似文献
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Shahnawaz Iram Siddiqui Mangey Ram Nagar Abhijeet Choudhury Jin-Tin Lin Dovydas Blazevicius Gintare Krucaite Saulius Grigalevicius Jwo-Huei Jou 《Molecules (Basel, Switzerland)》2021,26(24)
Low color temperature candlelight organic light-emitting diodes (LEDs) are human and environmentally friendly because of the absence of blue emission that might suppress at night the secretion of melatonin and damage retina upon long exposure. Herein, we demonstrated a lighting device incorporating a phenoxazine-based host material, 3,3-bis(phenoxazin-10-ylmethyl)oxetane (BPMO), with the use of orange-red and yellow phosphorescent dyes to mimic candlelight. The resultant BPMO-based simple structured candlelight organic LED device permitted a maximum exposure limit of 57,700 s, much longer than did a candle (2750 s) or an incandescent bulb (1100 s) at 100 lx. The resulting device showed a color temperature of 1690 K, which is significantly much lower than that of oil lamps (1800 K), candles (1900 K), or incandescent bulbs (2500 K). The device showed a melatonin suppression sensitivity of 1.33%, upon exposure for 1.5 h at night, which is 66% and 88% less than the candle and incandescent bulb, respectively. Its maximum power efficacy is 23.1 lm/W, current efficacy 22.4 cd/A, and external quantum efficiency 10.2%, all much higher than the CBP-based devices. These results encourage a scalable synthesis of novel host materials to design and manufacture high-efficiency candlelight organic LEDs. 相似文献
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Dr. Hong Huang Yixin Wang Biao Pan Xiao Yang Prof. Dr. Lei Wang Dr. Jiangshan Chen Prof. Dr. Dongge Ma Prof. Dr. Chuluo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1828-1834
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 (Tg) 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 (ηc,max) of 73.9 cd A?1, and a power efficiency (ηp,max) of 89.7 lm W?1. These results are among the best performances of [Ir(ppy)3]‐based devices with simple device configurations. 相似文献
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Chuanjun Wang Gaowen Liu Shaojie Liu Xunlu Zhang Changjin Ou Lu Wang Wei Sun Baoxiu Mi Juan Song Zhiqiang Gao 《中国化学》2016,34(8):763-770
A bipolar host material, 2,4,6‐tris(3‐(carbazol‐9‐yl)phenyl)‐triazine (TCPZ), was synthesized according to reported method. Due to the higher triplet energy compared to green and red phosphors, TCPZ is suitable to host them in phosphorescent organic light‐emitting diodes (PhOLEDs). Although the triplet of TCPZ is slightly lower than a common blue phosphor, good blue PhOLEDs using TCPZ as the host were successfully demonstrated in this work. By low temperature emission measurement, it was found that the energy splitting between the singlet and triplet of TCPZ is as small as 0.24 eV. Therefore, thermal activated energy transfer from triplet to singlet in the host TCPZ is expected to occur, which can be afterwards efficiently transferred to the blue phosphor, hence enabling it to host blue phosphor. As a result, TCPZ can be used as host for phosphors in panchromatic range. Additionally, single‐carrier devices clearly prove its good bipolar transport feature, beneficial to device performance. By using TCPZ as a host, high performance deep‐red, green and blue PhOLEDs have been achieved, with maximum efficiencies of 9.3 cd·A?1 (13.2%), 81.3 cd·A?1 (23.1%) and 17.03 cd·A?1 (10.4%), respectively. 相似文献