Influence of carrier-injection efficiency on modulation rate of organic light source

http://www.opticsinfobase.org/abstract.cfm?URI=ol-32-13-1905 | http://www.opticsinfobase.org/abstract.cfm?URI=ol-32-13-1905We have investigated the relationship between the energy levels of an emissive layer and the modulation rate of organic light-emitting diodes (OLEDs) based on a distyrylbenzene derivative, 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DSB). By utilizing DSB as an emitting material, a high modulation rate can be realized because of the short fluorescence lifetime of 0.2 ns of DSB. Furthermore, we also found that an energy gap between an emissive layer and an adjacent organic layer is an important parameter to improve modulation rate. DSB-doped 4,4-bis(2,2-ditolylvinyl)biphenyl is the best combination of all the organic materials used in this study, and the fastest cutoff frequency of 10 MHz has been achieved for the OLED in spite of the large emitting area of 1mm(2). (c) 2007 Optical Society ofAmerica.textapplication/pdfjournal articl

Transient response of blue organic electroluminescence devices with short fluorescence, lifetime of substituted phenyl/vinyl compound as an emissive layer

http://www.opticsinfobase.org/abstract.cfm?URI=ol-32-9-1150 | http://www.opticsinfobase.org/abstract.cfm?URI=ol-32-9-1150We have demonstrated a short fluorescence lifetime of the substituted phenyl/vinyl compound, 1,4-bis[2-[4-[N N-di(p-tolyl)amino]phertyl]vinyl]benzene (DSB). The fluorescence lifetime of the 0.5 mol.% DSB-doped 4,4'-bis(9-carbazolyl)biphenyl film is 1.2 ns, which is desirable for organic light-emitting diode (OLED) light sources for optical interconnect applications. We have also examined frequency dependences on the electroluminescence (EL) intensity of the OLED and the photoluminescence (PL) intensity of the DSB film. The -3 dB cutoff frequency of the EL intensity is about 3 MHz for the optimized device, and the -3 dB cutoff frequency of the PL intensity is about 160 MHz for the optically pumping DSB film. (c) 2007 Optical Society of America.textapplication/pdfjournal articl

Transient property of optically pumped organic film of different fluorescence lifetimes

http://link.aip.org/link/?APPLAB/90/231105/1 | http://link.aip.org/link/?APPLAB/90/231105/1The authors have investigated the direct relationship between the fluorescence lifetime (FL) and the transient photoluminescence (PL) response of organic materials to examine the applicability of organic light-emitting diodes as light sources for optical communications. Transient PL responses of organic materials with different FLs were measured as a frequency dependence of PL intensity pumped by a modulated violet laser diode. The authors have revealed that the cutoff frequency of PL intensity is significantly related to FL of an organic film. The -3 dB cutoff frequency of 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DSB) has reached about 160 MHz, which is much higher than that of other organic materials. This is because the FL of DSB is shortest among all the organic materials used in this study. (c) 2007 American Institute of Physics.textapplication/pdfjournal articl

Fast-response organic-inorganic hybrid light-emitting diode

We demonstrated important changes produced on the modulation frequency of hybrid organic-inorganic light-emitting diodes to examine the applicability as a light source for visible optical communications. The fabricated device,structure., was 4,4'-bis[N-(1-napthyl)-N-phenyl-amino]biphenyl/4,4'- (bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl:4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl/ZnS/LiF/MgAg. This device showed an, improvement in the modulation frequency using ZnS instead I of an organic material, tris (8-hydroxyquinoline)aluminum. A. maximum; cutoff frequency of 20.6 MHz was achieved.textapplication/pdfjournal articl

Transient characteristics of organic light-emitting diodes with efficient energy transfer in emitting material

http://www.sciencedirect.com/science/journal/00406090 | http://www.sciencedirect.com/science/journal/00406090We have investigated the combination effect of host–guest materials in an emitting layer on the transient property of an organic light-emitting diode (OLED). We found that an efficient energy transfer owing to the large overlap between the photoluminescence spectrum of host material and the absorption spectrum of guest material was an important factor to improve the response speed of the OLED. As a result, the rise time of optical response was mainly affected by the combination of host–guest materials, and it increased using the optimal guest material, 1,4-bis[2-[4-N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DSB). A maximum −3 dB cutoff frequency of 15.8 MHz was achieved for an OLED with DSB as a guest material.textapplication/pdfjournal articl

High coupling efficiency of microcavity organic light-emitting diode with optical fiber for as light source for optical interconnects

http://jjap.ipap.jp/link?JJAP/46/642/ | http://jjap.ipap.jp/link?JJAP/46/642/We investigated directional characteristics of the electroluminescence (EL) from microcavity organic light-emitting diodes (MOLEDs) to examine applicability of these diodes as a light source for optical interconnects. By measuring the angular dependence of a EL emission, we estimated the coupling efficiency between a MOLED and an optical fiber. The coupling efficiency was enhanced by 1.4-fold compared with that of a non cavity organic light-emitting diode (OLED), and reached 85% for an optical fiber with a numerical aperture (NA) of 0.5. The current efficiency of the MOLED also increased optimizing the device structure, and its maximum was 18.4 cd/A.textapplication/pdfjournal articl

Enhanced modulation speed of tris(8-hydroxyquinoline)aluminum-based organic light source with low-work-function electrode

http://jjap.ipap.jp/link?JJAP/46/7880/ | http://jjap.ipap.jp/link?JJAP/46/7880/We have investigated the effects of barrier height at a metal/organic interface on the modulation speed of organic light-emitting diodes (OLEDs). We found that a low barrier height is important for improving the modulation speed. Also, the insertion of an 8-hydroxyquinolinato lithium (Liq) layer as an electron injection layer (EIL) was observed to increase the modulation speed of OLEDs. As a result, the improved modulation speed was demonstrated using a low-work-function electrode and an EIL. We have ascribed the enhanced modulation speed of the OLEDs to current density-voltage characteristics. A maximum cutoff frequency of 12.1 MHz was achieved for an OLED with a Liq or Ca layer as an EIL and a metal cathode, respectively.textapplication/pdfjournal articl

静電噴霧法を用いた有機光電変換素子の効率向上に関する研究

若手展開研究: カテゴリBtextapplication/pdfresearch repor

ホスト情報管理システムUCANN

application/pdf総合情報センター年報情報. 2001, 7, p.83-91othe

ゾルゲルガラスを用いた白色LED 用窒化物蛍光体の信頼性向上

プロジェクト番号 : A09-36若手展開研究 : カテゴリBtextapplication/pdfresearch repor