Organic oxide/Al composite cathode in small molecular organic light-emitting diodes (original) (raw)
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Journal of Materials Science: Materials in Electronics, 2020
Organic light-emitting diodes (OLEDs) play a key role in modern display devices and systems. A highly desirable material for fabricating OLEDs is tris(8hydroxyquinoline)aluminum (Alq 3). In this work, a highly efficient OLED based on dysprosium (Dy)-incorporated Alq 3 (Alq 3-Dy) was fabricated. The fabricated OLED had four layers, namely, those of indium tin oxide (ITO), N, N 0-Di(1naphthyl)-N, N 0-diphenyl-(1,1 0-biphenyl)-4,4 0-diamine (NPB), Alq 3-Dy, and aluminum (Al). The ITO and Al layers were used as electrodes, while the NPB was selected as a hole transport layer. All the layers were deposited sequentially on a glass substrate. The surface morphologies of these layers clarified that the materials were deposited as nanosphere particles. The OLED performance showed significant improvement in terms of the operating voltage, current efficiency, and luminance of the fabricated Alq 3-Dy OLED compared with that of the pure Alq 3 OLED device. The luminance value was significantly enhanced from approximately 250 cd/m 2 for the pure Alq 3 OLED to approximately 5000 cd/m 2 for the Alq 3-Dy OLED. Moreover, the electroluminescence (EL) intensity of the Alq 3-Dy OLED was 20 times higher than that of the Alq 3 OLED. These findings may have a significant impact on the fabrication of the OLEDs and display devices.
NaCl/Ca/Al as an efficient cathode in organic light-emitting devices
Applied Surface Science, 2006
An efficient cathode NaCl/Ca/Al used to improve the performance of organic light-emitting devices (OLEDs) was reported. Standard N,N 0 -bis(1-naphthyl)-N,N 0 -diphenyl-1,1 0 biphenyl 4,4 0 -dimaine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq 3 ) devices with NaCl/Ca/Al cathode showed dramatically enhanced electroluminescent (EL) efficiency. A power efficiency of 4.6 lm/W was obtained for OLEDs with 2 nm of NaCl and 10 nm of Ca, which is much higher than 2.0 lm/W, 3.1 lm/W, 2.1 lm/ W and 3.6 lm/W in devices using, respectively, the LiF (1 nm)/Al, LiF (1 nm)/Ca (10 nm)/Al, Ca (10 nm)/Al and NaCl (2 nm)/ Al cathodes. The investigation of the electron injection in electron-only devices indicates that the utilization of the NaCl/Ca/Al cathode substantially enhances the electron injection current, which in case of OLEDs leads to the improvement of the brightness and efficiency. #
Recent advances in the electrical and optical properties of Alq 3 and Alq 3 derivatives based OLEDS
View the article online for updates and Paper • The following article isOpen access Recent advances in the electrical and optical properties of Alq3 and Alq3 derivatives based OLEDS Mrinmoy Debsharma1, Tanay Pramanik2, Chisomo Daka3 and Rupam Mukherjee1 Published under licence by IOP Publishing Ltd Journal of Physics: Conference Series, Volume 2267, 3rd International Conference on Recent Advances in Fundamental and Applied Sciences (RAFAS 2021) 24/06/2021 - 26/06/2021 Online Citation Mrinmoy Debsharma et al 2022 J. Phys.: Conf. Ser. 2267 012159 DOI 10.1088/1742-6596/2267/1/012159 DownloadArticle PDF Article metrics 740 Total downloads 44 total citations on Dimensions. Share this article Article and author information Abstract OLEDs (Organic light-emitting diodes) have become he most popular organic lighting-technology to fabricate full color, flexible, flat panel displays and various other lighting purposes in recent years. The greatest technical challenges so far in this area has been identified as finding new organic semiconducting electroluminescent materials with higher efficiency, longer durability and low operating voltage and long-term stability. Tris(8-hydroxyquino-linato) aluminium (Alq3) is one such promising material with an octahedral coordination che-lated aluminium (III) structure which has proved its versatile optical properties since long time. Alq3 is a typical electron transporting material used as electron transport layer (ETL)and also used as host material of emissive layer in organic light emitting diodes (OLEDs). In this review paper, our main focus is on recent advances in the optical and electrical properties of Alq3 and Alq3 derivatives-based OLEDs developed so far. On addition, we provide a comparison table of electroluminescence and photoluminescence performance and efficiency through EL spectra, PL spectra, Absorption spectra, Current-voltage plot data collected from different research groups all around the world.. You may also like Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
American Journal of Applied Sciences, 2010
ABSTRACT Problem statement: How the thickness of the tris (8-hydroxyquinolinato) Aluminum (Alq3) effect the optical and electrical properties of organic light emitting diode. Approach: The optimum thickness, photoluminescence and current-voltage characteristic of Alq3 layer on N, N-bis (inaphthyl)- N,N-diphenyl-1,1-biphenyl-4,4-diamine (55 nm) layer in Organic Light-Emitting Devices (OLED) structure are reported. Alq3 and NPB organic layers are used as Electron Transport Layer (ETL) and as Hole Transport Layer (HTL) in Organic Light-Emitting Devices (OLED). The thin layers of the NPB and Alq3 were prepared by thermal evaporation method. Results: The Alq3 layer was evaporated on the NPB layer for thickness ranging from 16 to 134 nm and photoluminescence and I-V characteristic were studied using fiber optics spectrophotometer (Ocean Optics- USB 2000 FLG) and current-voltage source (Keithley, model 2400). Conclusion: It was found that the Alq3 with 84 nm thicknesses gives the highest photoluminescence peak at 520 nm wavelengths, as well as the lowest turn on voltage of the device. The optical reflectance spectra for every sample were also reported.
Applied Physics …, 2008
We have demonstrated an organic light-emitting diode based on molybdenum oxide ͑MoO x ͒ doped 4,4Ј ,4Љ-tris͑3-methylphenylphenylamino͒triphenylamine ͑m-MTDATA͒ as a p-type doping hole injection layer. The tris-͑8-hydroxyquinoline͒ aluminum ͑Alq 3 ͒-based organic light-emitting diodes show high brightness at very low operating voltage, 100 cd/ m 2 at 3.2 V and 1000 cd/ m 2 at 4.4 V, corresponding to a low turn-on voltage of 2.4 V. Such improved properties are attributed to the formation of the charge transfer complex produced by doping MoO x into m-MTDATA, which provides much more free hole carriers, and the introduction of an efficient electron-injecting layer to improve the performance.
Thin Solid Films, 2010
a b s t r a c t on electron injection and device performance in organic light-emitting diodes based on tris-(8hydroxyquinoline) aluminum, were investigated systematically. The insertion of the buffer layers at the organic/cathode interface not only reduced the operating voltage, but also enhanced the luminance and efficiency, which is attributed to the improvement of electron injection efficiency. It was found that the efficiency of the electron injection was closely related to the inherent properties of the buffer layer, such as its melting point (MP) and dielectric constant (ε), as well as with the buffer layer's interface with the metallic electrode through the effective work function (WF). Low MP, low ε and low WF values result in an effective improvement in the injection of the electrons, and thus to the device performance. The electroluminescent performance was further improved by the introduction of calcium between the buffer layer and the aluminum electrode.
Applied Physics Letters, 2011
Efficient indium tin oxide (ITO)-free small molecule organic light-emitting diodes (SMOLEDs) with multilayered highly conductive poly(3,4-ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS) as the anode are demonstrated. PEDOT:PSS/MoO 3 /N,N 0 -diphenyl-N,N 0 -bis (1-naphthylphenyl)-1,1 0 -biphenyl-4,4 0 -diamine (NPD)/tris(8-hydroxyquinoline) Al (Alq 3 )/4,7-diphenyl-1,10-phenanthroline (BPhen)/LiF/Al SMOLEDs exhibited a peak power efficiency of 3.82 lm/W, 81% higher than that of similar ITO-based SMOLEDs (2.11 lm/W). The improved performance is believed to be due to the higher work function, lower refractive index, and decreased surface roughness of PEDOT:PSS vs ITO, and to Ohmic hole injection from PEDOT:PSS to the NPD layer via the MoO 3 interlayer. The results demonstrate that PEDOT:PSS can substitute ITO in SMOLEDs with strongly improved device performance.
Electron-injecting properties of Rb2CO3-doped Alq3 thin films in organic light-emitting diodes
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013
Rubidium carbonate (Rb 2 CO 3)-doped tris(8-quinolinolato)aluminum (III) (Alq 3) thin films have been investigated as electron-injecting materials for organic light-emitting diodes (OLEDs). Electron-only devices consisting of glass/tin-doped indium oxide (ITO)/Rb 2 CO 3-doped Alq 3 (10 nm)/aluminum (Al) showed an electron-ohmic contact property between the electrode and the organic layer at the doping concentration of 10% and higher. The electron-injecting ability of these contacts was largely enhanced by the n-doping effect of Rb 2 CO 3 into the Alq 3 layer. The ultraviolet photoemission spectra revealed that when the doping concentration was increased, the n-doping effect reduced the carrierinjecting barrier height by lowering the work function at the Rb 2 CO 3-doped Alq 3 interfaces. Also, the x-ray photoemission spectra showed that as the doping concentration was increased at the interfaces, Alq 3 molecules decomposed in a chemical reaction with Rb 2 CO 3. The OLED device, having the glass/ITO/molybdenum oxide (MoO x , 25%)-doped N,N 0-diphenyl-N,N 0-bis(1-naphthyl)-1,1 0-biphenyl-4,4 0-diamine (NPB, 5 nm)/NPB (63 nm)/Alq 3 (32 nm)/Rb 2 CO 3-doped Alq 3 (10%, 10 nm)/Al (100 nm) structure, showed the best performance at the optimal doping concentration of Rb 2 CO 3-doped Alq 3 , both the maximum luminance of 114 400 cd/m 2 at the bias voltage of 9.8 V and the power efficiency of 2.7 lm/W at the luminance of 1000 cd/m 2 were obtained. V