Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education

Beijing, China

Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education

Beijing, China
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Li Y.,Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education | Li Y.,Tsinghua University | Zhang D.,Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education | Zhang D.,Tsinghua University | And 6 more authors.
Science China Chemistry | Year: 2016

High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors’ concentration and efficiency roll-off of PHOLEDs. In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-ll-yl)-l,3,5-triazine (BCPICT), with thermally activated delayed fluorescent (TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%. When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m2. © 2016, Science China Press and Springer-Verlag Berlin Heidelberg.


Haoyuan L.,Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education | Haoyuan L.,Tsinghua University | Liang C.,Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education | Liang C.,Tsinghua University | And 12 more authors.
Science China Chemistry | Year: 2012

The hole and electron mobilities of the amorphous films of the organic semiconductor 4,4'-N,N'-dicarbazole-biphenyl (CBP) at different electric fields were measured through the time of flight (TOF) method. Based on its crystalline structure, the hole and electron mobilities of CBP were calculated. A detailed comparison between experimental and theoretical results is necessary for further understanding its charge transport properties. In order to do this, charge mobilities at zero electric field, 7mu;(0), were deduced from experimental data as a link between experimental and theoretical data. It was found that the electron transport of CBP is less affected by traps compared with its hole transport. This unusual phenomenon can be understood through the distributions of frontier molecular orbitals. We showed that designing materials with frontier molecular orbitals localized at the center of the molecule has the potency to reduce the influence of traps on charge transport and provide new insights into designing high mobility charge transport materials. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.


Miao Y.,Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education | Xie K.,Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education | Xiang Q.,Key Laboratory For Optoelectronics And Communication Of Jiangxi Provincejiangxi Science And Technology Normal Universitynanchang330013Pr China | Xiong Z.,Key Laboratory For Optoelectronics And Communication Of Jiangxi Provincejiangxi Science And Technology Normal Universitynanchang330013Pr China | And 2 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2016

In this work, Li:Mg alloys are formed by co-evaporation of Li3N and Mg with different ratios and are used as cathode for organic light-emitting didoes (OLEDs). Three phases of Li:Mg alloys can be observed by XRD measurements for Li:Mg alloys with 5, 20, and 50% molar ratio of Li, respectively. The XPS result reveals the charge transfer between Li and Mg, further confirming the formation of Li:Mg alloy. OLEDs with Li:Mg alloy as the cathode all show lower operating voltages and higher efficiencies than the control device using Mg:Ag cathode. For the Li:Mg alloy with 20% Li, the peak power efficiency is 2.23lmW-1, which is more than doubled compared with the control device (1.09lmW-1). Quantum calculation has been carried out to get the surface work functions of different Li:Mg alloys. The 20% Li doped Li:Mg alloy possesses the lowest work function of 2.497eV, leading to the lowest electron injection barrier and best device performance. We also find that the surface work function of the Li:Mg alloy would be affected by not only aggregation phase but also the surface distribution of crystal facets (preferential crystal orientation), which indicates that alloys showed anisotropy in work function, like elemental metals. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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