Wide-range work-function tuning of active graphene transparent electrodes via hole doping
2016
Syu, Jheng-Yuan | Chen, Yu-Min | Xu, Kai-Xiang | He, Shih-Ming | Hung, Wu-Ching | Chang, Chien-Liang | Su, Ching-Yuan
Graphene is regarded as a potential candidate to replace the transparent conductive (TC) electrodes that are currently used in various optoelectronic applications. However, there is still a lack of methods by which to achieve low sheet resistance (Rₛ) with stable doping and work functions with a wide range of tunability, which is significant for band alignment at the interface to enhance charge transport and thus to achieve higher device performance. We developed a novel strategy for preparing a TC electrode by doping layer-by-layer (LBL)-stacked graphene with AuCl₃, by which means an excellent TC performance (an Rₛ of 40 ohm sq⁻¹ at a transmittance (T) of 89.5%) and an extremely wide range of work-function tunability (∼1.5 eV) were successfully achieved. Moreover, a hybrid electrode prepared by transferring doped graphene onto a pre-patterned Cu metal mesh exhibited a low resistance of ∼4.9 ohm sq⁻¹. In addition, we monitored the long-term stability of AuCl₃-doped graphene for 6 months and also constructed a model for accelerated degradation testing. The relevant mechanism of charge transfer between the graphene and the dopants was characterized based on X-ray photoelectron spectroscopy (XPS) spectra to elucidate degradation observed after long-term testing. This work contributes a novel type of “active electrode”; the doped graphene film not only serves as a high-performance TC electrode but also provides a wide range of tunable work functions. The proposed active electrode is prepared using a scalable and facile doping process, which paves the way for its usage in applications such as optoelectronic devices.
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