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Park J.,Center for Superfunctional Materials | Lee W.H.,Pohang University of Science and Technology | Huh S.,Center for Superfunctional Materials | Sim S.H.,SKKU Advanced Institute of Nanotechnology SAINT | And 6 more authors.
Journal of Physical Chemistry Letters | Year: 2011

We have devised a method to optimize the performance of organic field-effect transistors (OFETs) by controlling the work functions of graphene electrodes by functionalizing the surface of SiO2 substrates with self-assembled monolayers (SAMs). The electron-donating NH2- terminated SAMs induce strong n-doping in graphene, whereas the CH 3-terminated SAMs neutralize the p-doping induced by SiO2 substrates, resulting in considerable changes in the work functions of graphene electrodes. This approach was successfully utilized to optimize electrical properties of graphene field-effect transistors and organic electronic devices using graphene electrodes. Considering the patternability and robustness of SAMs, this method would find numerous applications in graphene-based organic electronics and optoelectronic devices such as organic light-emitting diodes and organic photovoltaic devices. © 2011 American Chemical Society.


Kang B.,Ulsan National Institute of Science and Technology | Choi Y.,Ulsan National Institute of Science and Technology | Kim B.-S.,Ulsan National Institute of Science and Technology | Youn I.S.,Center for Superfunctional Materials | Lee G.,Ulsan National Institute of Science and Technology
Carbon | Year: 2016

Using the first principles methods, we performed systematic study on the effect of edge-functional groups on the electronic energy levels and the optical properties of sp2 carbon clusters. It is found that the intrinsic π and π∗ orbitals are weakly altered by oxygen-bearing functional groups, but it is significantly disrupted by pyrrolic groups. Thereby the oscillator strength of the lowest-energy transition is found to be much stronger for the pyrrolic group functionalized cluster than for the carboxyl group. From our results being consistent with the experimental reports, we suggest that the photoluminescence enhancement is caused by a perturbation of the intrinsic frontier molecular orbitals by edge groups. © 2016 Elsevier Ltd

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