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강유진,이준엽 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
High triplet energy electron transport materials with dibenzothiophene and dibenzofuran core modified with a diphenyltriazine unit were developed. The two exciton blocking materials showed high triplet energy above 2.80 eV by stable aromatic units in molecular structure. Small dihedral angle between aromatic moieties allowed them to maintain the lifetime of the reference device without the exciton blocking layer. These materials enhanced maximum quantum efficiency from 8.3% to 13.0% by inserting the exciton blocking layers.
Kang, Yu Jin,Lee, Jun Yeob Elsevier 2016 Organic electronics Vol.32 No.-
<P><B>Abstract</B></P> <P>High triplet energy electron transport materials with dibenzothiophene and dibenzofuran cores modified with a diphenyltriazine unit were investigated as electron transport type exciton blocking materials for stable blue phosphorescent organic light-emitting diodes. The two exciton blocking materials showed high triplet energy above 2.80 eV and enhanced quantum efficiency of the blue phosphorescent devices by more than 40% while maintaining stability of the pristine blue devices without the high triplet energy exciton blocking layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High triplet energy electron transport materials derived from diphenyltriazine electron transport moiety. </LI> <LI> Dibenzothiophene and dibenzofuran derived exciton blocking materials for blue phosphorescent devices. </LI> <LI> Thermally stable exciton blocking materials for stable lifetime of the blue phosphorescent organic light-emitting diodes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
최정민,이준엽 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Blue phosphorescent organic light-emitting diodes (PHOLEDs) with high efficiency and lifetime were developed by exciton harvesting layer at electron transport layer. A green emitter doped electron transport layer was able to harvest the triplet exciton in the blue PHOLEDs, which improved the lifetime and the efficiency of the blue PHOLEDs compared with a common electron transport layer. The exciton harvesting layer blocked blue triplet emitter from triplet exciton quenching.
Rhee, Sang Ho,Yook, Kyoung Soo,Kim, Sung Hyun,Ryu, Seung Yoon The Electrochemical Society 2016 ECS journal of solid state science and technology Vol.5 No.2
<P>The structural change with the different location of exciton blocking layer's (EBL) in blue phosphorescent organic light-emitting diodes (PHOLEDs) were investigated, where N, N'-dicarbazolyl-3,5-benzene (mCP) with high triplet bandgap was used as the EBL. The change of recombination zone (RZ) were originated from the different formation of triplet excitons depending on the EBL location between hole/electron transporting layer (HTL/ETL) and emission layer (EML), resulting in the variation of the device performance and generating an optical micro-cavity effect in the electroluminescence (EL) spectrum around 500 nm. The device using the EBL between the HTL and the EML showed the highest device performance due to the good charge balance, avoiding the serious triplet exciton quenching and the reduced micro-cavity effect. (C) 2015 The Electrochemical Society. All rights reserved.</P>
Efficient Carrier and Exciton Confinement in White Phosphorescent Organic Light-emitting Diodes
이석재,구자룡,신현수,김영관,이금희,윤승수 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.10
We demonstrated that luminous- and external quantum-efficiencies of white phosphorescent organic light emitting diodes (PHOLEDs) were improved by a device architecture which confines the carriers and excitons inside an emitting layer (EML). Two white PHOLEDs were fabricated with a commercially available red-phosphorescence emitter; bis(2-phenylquinolinato)-acetylacetonate iridium III (Ir(pq)<SUB>2</SUB>acac) doped in N,N’-dicarbazolyl-3,5-benzene (mCP) and a blue-phosphorescence emitter; bis(3,5-Difluoro-2-(2- pyridyl)phenyl-(2-carboxypyridyl) iridium III (FIrpic) doped in p-bis(triphenylsilyly)benzene (UGH2), as red/blue emitting layers. In addition, both devices (devices A and B) have a triplet exciton blocking layer (TEBL) in hole transporting layer (HTL) side, using the high triplet state material to get high efficiency. Device B, which has one more buffer layer of <I>p</I>-type 4,4’,4’’-tri(N-carbazolyl) triphenylamine (TCTA) material between the HTL and TEBL. The properties of device B exhibited maximum luminous efficiency and external quantum efficiency of 22.77 cd/A and 11.5 %, respectively, were found to be superior to the device A. It also showed white emission with CIE<SUB>X,Y</SUB> coordinates of (x=0.33, y=0.37) at 8 V.
오현석,이준웅,Oh, Hyun-Seok,Lee, Joon-Ung 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.12
Photovoltaic effects in organic solar cell were studied in a cell configuration of ITO/PEDOT:PSS/CuPc(20 nm)/$C_{60}$(40 nm)/BCP/Al(150 nm) at room temperature. Here, the BCP layer works as an exciton blocking layer. The exciton blocking layer must transport electrons from the acceptor layer to the metal cathode with minimal increase in the total cell series resistance and should absorb damage during cathode deposition. Therefore, a proper thickness of the exciton blocking layer is required for an optimized photovoltaic cell. Several thicknesses of BCP were made between $C_{60}$ and Al. And we obtained characteristic parameters such as short-circuit current, open-circuit voltage, and power conversion efficiency of the device under the illumination of AM 1.5.
Kim, I.,Fleetham, T.,Choi, H.w.,Choi, J.Y.,Lee, T.S.,Jeong, D.S.,Lee, W.S.,Lee, K.S.,Lee, Y.K.,Alford, T.L.,Li, J. Elsevier Science 2014 ORGANIC ELECTRONICS Vol.15 No.10
We demonstrate the power conversion efficiency of bulk heterojunction organic solar cells can be enhanced by introducing Ag nanoparticles into organic exciton blocking layer. The Ag nanoparticles were incorporated into the exciton blocking layer by thermal evaporation. Compared with the conventional cathode contact materials such as Al, LiF/Al, devices with Ag nanoparticles incorporated in the exciton blocking layer showed lower series resistances and higher fill factors, leading to a 3.2% power conversion efficiency with a 60nm active layer; whereas, the conventional devices have only 2.0-2.3% power conversion efficiency. Localized surface plasmon resonances by the Ag nanoparticles and their contribution to photocurrent were also discussed by simulating optical absorptions using a FDTD (finite-difference-time-domain) method.
Jeon, S.K.,Lee, J.Y. Elsevier Science 2015 ORGANIC ELECTRONICS Vol.27 No.-
Lifetime of blue phosphorescent organic light-emitting diodes (OLEDs) was improved by suppressing a recombination zone shift using a high triplet energy exciton blocking layer. Host material of the emitting layer was inserted as the exciton blocking layer between a hole transport layer and an emitting layer, and the exciton blocking layer kept the recombination zone near hole transport layer side without significant emission zone change during lifetime test. The suppressed recombination zone shift improved the lifetime of the blue phosphorescent OLED by four times.
Chin, B. D.,Lee, C. WILEY-VCH Verlag 2007 Advanced Materials Vol.19 No.16
<B>Graphic Abstract</B> <P>Charge-carrier and exciton confinement is essential for efficiency and stability enhancment of electrophosphorescent devices. Emission-layer lifetimes of a 4,4′-N,N′-dicarbazole-biphenyl host doped with either a red- or green- emitting dye (upper and lower figures) show a strong dependence and near independence, respectively, on the type of exciton blocking layer used (four are shown). This is explained using energy- level differences and corresponding charge-trapping behavior. <img src='wiley_img/09359648-2007-19-16-ADMA200602509-content.gif' alt='wiley_img/09359648-2007-19-16-ADMA200602509-content'> </P>