Limits...
Solution-processed transparent blue organic light-emitting diodes with graphene as the top cathode.

Chang JH, Lin WH, Wang PC, Taur JI, Ku TA, Chen WT, Yan SJ, Wu CI - Sci Rep (2015)

Bottom Line: However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics.The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes.With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 106, R.O.C.

ABSTRACT
Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency. Recently, organic light-emitting diodes (OLEDs)have been successfully demonstrated to possess high luminous efficiencies with p-doped graphene anodes. However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics. In this paper, we demonstrate fully solution-processed OLEDs with n-type doped multilayer graphene as the top electrode. The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes. With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

No MeSH data available.


Related in: MedlinePlus

The schematic illustration and characteristics of n-type doped graphene films.(a) The schematic illustration of CsF-doped graphene multilayer. (b) Sheet resistance and transmittance at 500 nm of pristine () and CsF-doped () graphene with number of layers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4402614&req=5

f2: The schematic illustration and characteristics of n-type doped graphene films.(a) The schematic illustration of CsF-doped graphene multilayer. (b) Sheet resistance and transmittance at 500 nm of pristine () and CsF-doped () graphene with number of layers.

Mentions: To enhance the electrical properties of graphene as applied in organic devices, we increase the number of graphene layers. Moreover, to maintain the lower work function properties, graphene is n-doped during every transfer process. As shown in Fig. 2a, Cs atoms are intercalated between every graphene layer to form n-type doped multilayer graphene films. The sheet resistance and transmittance with varying numbers of graphene layers on glass are investigated as shown in Fig. 2b. The transmittances at a wavelength of 500 nm of one-, two-, three- and four-layer pristine graphene samples are 96.8%, 93.9%, 91.2%, and 88.6%, respectively. At the same time, the sheet resistance values of one- to four-layer pristine graphene films are 1892, 666, 484, and 270 ω/sq, respectively. As the number of layers increases, the transmittance and sheet resistance decrease. The optical transmittance of graphene films is reduced by around 2.2–2.3% for each additional layer, and the overall conductivity of the graphene films increases as the number of stacked layer increase2021. On the other hand, the transmittances of one- to four-layer CsF-doped graphene films are 95.4, 93.6, 89.9, and 84.9%, respectively. It is noted that the transmittance drops to 84.9% with a four-layer CsF-doped graphene film, a value similar to that reported for multilayer graphene doped with 2,3,5,6-Terafluoro-7,7,8,8-teracyanoquinodimethane (F4-TCNQ)22. The sheet resistances of one- to four-layer CsF-doped graphene films are 2515, 770, 290, and 118 ω/sq, respectively. The sheet resistance of CsF-doped monolayer graphene is higher than that of pristine monolayer graphene because a multilayer graphene structure is needed to form layer-by-layer intercalations of graphene and Cs atoms for effective doping. Therefore, conductivity is distinctly enhanced with increasing numbers of graphene layers.


Solution-processed transparent blue organic light-emitting diodes with graphene as the top cathode.

Chang JH, Lin WH, Wang PC, Taur JI, Ku TA, Chen WT, Yan SJ, Wu CI - Sci Rep (2015)

The schematic illustration and characteristics of n-type doped graphene films.(a) The schematic illustration of CsF-doped graphene multilayer. (b) Sheet resistance and transmittance at 500 nm of pristine () and CsF-doped () graphene with number of layers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4402614&req=5

f2: The schematic illustration and characteristics of n-type doped graphene films.(a) The schematic illustration of CsF-doped graphene multilayer. (b) Sheet resistance and transmittance at 500 nm of pristine () and CsF-doped () graphene with number of layers.
Mentions: To enhance the electrical properties of graphene as applied in organic devices, we increase the number of graphene layers. Moreover, to maintain the lower work function properties, graphene is n-doped during every transfer process. As shown in Fig. 2a, Cs atoms are intercalated between every graphene layer to form n-type doped multilayer graphene films. The sheet resistance and transmittance with varying numbers of graphene layers on glass are investigated as shown in Fig. 2b. The transmittances at a wavelength of 500 nm of one-, two-, three- and four-layer pristine graphene samples are 96.8%, 93.9%, 91.2%, and 88.6%, respectively. At the same time, the sheet resistance values of one- to four-layer pristine graphene films are 1892, 666, 484, and 270 ω/sq, respectively. As the number of layers increases, the transmittance and sheet resistance decrease. The optical transmittance of graphene films is reduced by around 2.2–2.3% for each additional layer, and the overall conductivity of the graphene films increases as the number of stacked layer increase2021. On the other hand, the transmittances of one- to four-layer CsF-doped graphene films are 95.4, 93.6, 89.9, and 84.9%, respectively. It is noted that the transmittance drops to 84.9% with a four-layer CsF-doped graphene film, a value similar to that reported for multilayer graphene doped with 2,3,5,6-Terafluoro-7,7,8,8-teracyanoquinodimethane (F4-TCNQ)22. The sheet resistances of one- to four-layer CsF-doped graphene films are 2515, 770, 290, and 118 ω/sq, respectively. The sheet resistance of CsF-doped monolayer graphene is higher than that of pristine monolayer graphene because a multilayer graphene structure is needed to form layer-by-layer intercalations of graphene and Cs atoms for effective doping. Therefore, conductivity is distinctly enhanced with increasing numbers of graphene layers.

Bottom Line: However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics.The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes.With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 106, R.O.C.

ABSTRACT
Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency. Recently, organic light-emitting diodes (OLEDs)have been successfully demonstrated to possess high luminous efficiencies with p-doped graphene anodes. However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics. In this paper, we demonstrate fully solution-processed OLEDs with n-type doped multilayer graphene as the top electrode. The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes. With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

No MeSH data available.


Related in: MedlinePlus