Research Quantum Materials and Devices Laboratory

Research Topics

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Human-friendly Electronics : Flexilbe/Stretchable Displays and Electornics

Flexible/Stretchable Displays

Graphene and 2D materials have attracted great attentions because of their potential to overcome the limitations in electronics and many other technological fields. One of the most pursuing goals of my research team is to realize high-performance electronics from atomic/molecular-scale nanomaterials for these applications. Although the study is still in an infant stage, we are expecting to see a great success in a near future.

Two-dimensional (2D) materials have attracted significant attention because of their outstanding electrical, mechanical, and optical characteristics. Because all of the conducting (graphene), semiconducting (molybdenum disulfide, MoS2), and insulating (hexagonal boron nitride, h-BN) components can be constructed from 2D materials, thin-film transistors based on 2D materials (2D TFTs) have been developed. However, scaling-up is necessary for these technologies to go beyond their initial implementation using the mechanical exfoliation method. Furthermore, it would be beneficial to find a method to realize high flexibility and/or transparency to their full potential. In 2020, we developed large-sacle, flexible, and transparent 2D TFTs and demonstrated as a backplane in active-matrix organic light-emitting diodes (AMOLEDs).

In particular, the integration of graphene and TMDCs enables the implementation of 2D materials-based thin-film transistors (TFTs) in stretchable displays, given that TFTs are the fundamental element of various modern devices. , the mechanisms leading to TFT performance degradation are investigated, as they relate to the change in the contact resistance that is closely associated with the relative deformation of 2D materials under mechanical stress. Therefore, the synergetic integration of 2D materials with versatile electrical properties provides an important strategy for creating 2D materials-based stretchable TFTs, thus extending the excellent potential of 2D materials as innovative materials for stretchable active-matrix displays.

Graphene Electrode

Graphene produced by chemical vapor deposition (CVD) has attracted great interest as a transparent conducting material, due to its extraordinary characteristics such as flexibility, optical transparency, and high conductivity, especially in next-generation displays. Graphene-based novel electrodes have the potential to satisfy the important factors for high-performance flexible organic light-emitting diodes (OLEDs) in terms of sheet resistance, transmit-tance, work function, and surface roughness.

Flexible and trans-parent graphene electrode architecture is proposed by adopting a selective defect healing technique for CVD-grown graphene, which results in several benefits that produce high-performance devices with excellent stabilities. The proposed architecture, which has a multi-layer graphene structure treated by a layer-by-layer healing process, exhibits significant improvement in sheet resistance with high optical transparency. For improving the charge transport property and mechanical robustness, various defect sites of the CVD-grown graphene are successfully decorated with gold nanoparticles through a simple electroplating (EP) method. Further, a graphene-based OLED device that integrates the proposed electrode architecture on flexible substrates is demonstrated. Therefore, this architecture provides a new strategy to fabri-cate graphene electrode in OLEDs, extending graphene’s immense potential as an advanced conductor toward high-performance, flexible, and transparent displays.

Our group is researching various electronic device applications using CVD-grown graphene as an electrode.