A high performance inverted organic light emitting diode using an electron transporting material with low energy barrier for electron injection

Lee, Jeong‐Hwan; Wang, Po-Sheng; Park, Hyung-Dol; Wu, Chih-I; Kim, Jang‐Joo

doi:10.1016/j.orgel.2011.07.015

Cited by 68 publications

(24 citation statements)

References 26 publications

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“…In the as-deposited MoO 3 films, Mo (3d 5/2 ) and Mo (3d 3/2 ) states are shown at binding energies of 232.6 eV and 235.7 eV, respectively, indicating a domination of Mo 6þ oxidation states in the core level spectra. 25 After annealing, additional features are grown in the lower binding energy side and become pronounced when the temperature reaches 300 C. We deduce a Mo 3d 5/2 component at 231.8 eV, by deconvolution of the spectra, which represents reduced oxidation states of molybdenum atoms as compared to the non-annealed films. The binding energy of 231.8 eV is between that of Mo 6þ (3d 5/2 ) states at 232.6 eV and Mo 5þ (3d 5/2 ) states at 231.1 eV.…”

Section: Resultsmentioning

confidence: 80%

Enhancing the incorporation compatibility of molybdenum oxides in organic light emitting diodes with gap state formations

Wang

Tseng

et al. 2013

Journal of Applied Physics

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The enhancement of injection current and luminance in organic light emitting diodes is achieved by annealing molybdenum oxide (MoO 3 ) hole injecting layers prior to the deposition of hole transport layers. While there is no benefit by the incorporation of non-annealed MoO 3 in devices using 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) as the hole transport layers, the annealed MoO 3 layers exhibit a significant improvement in hole injection from indium tin oxide anodes to TAPC. X-ray photoemission spectroscopy reveals the change of oxidation states of Mo atoms in MoO 3 films due to the annealing process. The gap state formation is verified by ultra-violet photoemission spectroscopy. A more energetically favorable band alignment is obtained at the interface between the annealed MoO 3 and TAPC, resulting in improved hole injection efficiency. The overall performance of OLEDs can be enhanced by adopting annealed MoO 3 in most of the hole transport layers. V C 2013 AIP Publishing LLC. [http://dx.

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Section: Resultsmentioning

confidence: 80%

Enhancing the incorporation compatibility of molybdenum oxides in organic light emitting diodes with gap state formations

Wang

Tseng

et al. 2013

Journal of Applied Physics

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“…This is further evidence that a large difference in the LUMO levels can affect DC18's function as an electron injection layer, thus a double ETL using a second material with a better matched energy level to polymers with low LUMOs would enhance efficiency even further. Double ETLs have been used to address energy level mismatch before with excellent results, [40] and we are currently investigating similar methods for our material.…”

Section: Resultsmentioning

confidence: 99%

Solution processed naphthalene diimide derivative as electron transport layers for enhanced brightness and efficient polymer light emitting diodes

et al. 2013

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Increasing the efficiency and lifetime of polymer light emitting diodes (PLEDs) requires a balanced injection and flow of charges through the device, driving demand for cheap and effective electron transport/ hole blocking layers. Some materials, such as conjugated polyelectrolytes, have been identified as potential candidates but the production of these materials requires complex, and hence costly, synthesis routes. We have utilized a soluble small molecule naphthalene diimide derivative (DC18) as a novel electron transport/hole blocking layer in common PLED architectures, and compared its electronic properties to those of the electron transport/hole blocking small molecule bathocuproine (BCP). PLEDs incorporating DC18 as the electron transport layer reduce turn on voltage by 25%; increase brightness over three and a half times; and provide a full five-fold enhancement in efficiencies compared to reference devices. While DC18 has similar properties to the effective conjugated polyelectrolytes used as electron transport layers, it is simpler to synthesise, reducing cost while retaining favourable electron transport properties, and improves upon their degree for efficiency enhancement. The impact on device lifetime is hypothosized to be significant as well, due to the air-stability seen in many naphthalene diimide derivatives.

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“…4 shows the energy-band diagrams of (a) the typical CGL composed of BEDT-TTF-doped TPBi and HAT-CN and of (b) the hybrid CGL composed of BEDT-TTF-doped TPBi, mCP, and HAT-CN. The energy gaps of TPBi, HAT-CN, NPB, and mCP, as determined from the photoluminescence and the ultraviolet-visible absorption spectra, are 3.5, 3.9, 4.0, and 3.5 eV, respectively [20][21][22][23]. The efficiency enhancement mechanisms of the hybrid CGL in tandem OLEDs can be described on the basis of the energy-band diagrams.…”

Section: Methodsmentioning

confidence: 99%

Efficiency enhancement in tandem organic light-emitting devices with a hybrid charge generation layer composed of BEDT-TTF-doped TPBi/mCP/HAT-CN

Kim

2014

Organic Electronics

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A high performance inverted organic light emitting diode using an electron transporting material with low energy barrier for electron injection

Cited by 68 publications

References 26 publications

Enhancing the incorporation compatibility of molybdenum oxides in organic light emitting diodes with gap state formations

Enhancing the incorporation compatibility of molybdenum oxides in organic light emitting diodes with gap state formations

Solution processed naphthalene diimide derivative as electron transport layers for enhanced brightness and efficient polymer light emitting diodes

Efficiency enhancement in tandem organic light-emitting devices with a hybrid charge generation layer composed of BEDT-TTF-doped TPBi/mCP/HAT-CN

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