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.
Highlights
Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency
With n-doped graphene layers used as the top cathode, all-solution processed transparent organic light-emitting diodes (OLEDs) can be fabricated without any vacuum process
Polymer OLEDs are usually built by solution processes, such as spin-coating[3,4], ink-jet printing[5], screen printing[6], blade coating[7], or dipcoating[8], which enable much cost-effective device manufacture are more suitable for flexible electronic applications[9]
Summary
The work function of pristine graphene film is around 4.4 eV19, which is too high to reduce the energy barrier of electron injection from the cathode to the organic layers in devices. The injection barrier of electrons from the cathode is reduced with CsF-doped graphene (3.2 eV), and more electrons can be injected from graphene into the organic layer to increase current density This enhancement is consistent with the previous UPS results. A new polymer-free transfer method has been demonstrated to be an efficient way to modify the work function and sheet resistance of graphene, and n-type doped multilayer graphene films obtained using this method can be used as cathodes in OLEDs. we have provided a way to produce a transparent OLED with truly all-solution processes, including multilayer. Graphene electrodes can be used in a wide variety of organic optoelectronics with more efficient doping and simple transfer techniques
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