Optimizing the Propeties of Large-Area Graphene for High-Performance Transparent Electrodes

Abstract

In chapter 1, briefly introduce the 2D materials that have been intensively studied as emerging materials for future electronics, including flexible electronics, photonics, and electrochemical energy storage devices. Among representative 2D materials (such as graphene, boron nitride, and transition metal dichalcogenides) that exhibit extraordinary properties, graphene stands out in the flexible electronics field due to its combination of high electron mobility, high thermal conductivity, high specific surface area, high optical transparency, excellent mechanical flexibility, and environmental stability. Cu catalyst etching is one of the key processes to produce large-area graphene through chemical vapor deposition (CVD), which is needed to remove Cu catalysts and transfer graphene onto target substrates for further applications. Chapter 2 introduce that the addition of metal-chelating agents such as benzimidazole (BI) to etching solution. The resulting graphene film prepared by Cu stabilizing agent exhibits a low sheet resistance without additional doping processes. It also confirmed that such strong doping effect is stable enough to last for more than 10 months under ambient conditions due to the barrier properties of graphene. Chapter 3 introduce an ultraclean, cost-effective, and easily scalable method of transferring and patterning graphene using pressure sensitive adhesive films (PSAFs) at room temperature. This transfer is enabled by the difference in wettability and adhesion energy of graphene with respect to PSAF and a target substrate. The PSAF transferred graphene is found to be free from residues, and shows excellent charge carrier mobility with less doping effect compared to the other polymer supported methods. In addition, the sheet resistance of graphene transferred by recycled PSAF does not change considerably up to 4 times. Chapter 4 introduce the 0-dimensional graphene quantum dots (GQDs) that have been widely exploited due to tunable optical and electronic properties. Moreover, the dispersibility of GQDs can be controlled by chemical functionalization. A surface-engineered GQD in hole extraction polymer photovoltaic device shows enhanced power conversion efficiency (PCE) leading to significantly improved short circuit current density (Jsc) value. To maximize the PCE of the device, hydrophobic reduced GQDs were additionally incorporated in a bulk-heterojunction layer, which is found to promote a synergistic effect with the GQD-incorporated hole extraction layer.