Two-step process crops transparent graphene substitute
A team of researchers from Korea Institute of Science and Technology (KIST) has developed a carbon material that exhibits graphene characteristics but without the artificial defects usually found during its production. This material is positioned as a substitute for graphene in solar cells and semiconductor chips, as well as the solution to the key bottleneck in scaling graphene production.
The research team developed carbon nanosheet in a two-step process, which consists of coating the substrate with a polymer solution and heating. Considering that the existing process consists of eight steps to manufacture graphene, the new method makes it much simpler.
The new method easily controls the unwanted effects from the electronic and optical characteristics of carbon nanosheet, which is produced when the polymer solution is concentrated. As the molecule solution concentration gets higher [Axis X, (b), (c)], the thicker it gets (b) but also becomes less resistant (c), bringing about a better flow of current.
Figure 1: Two-step manufacturing process: (a) Quartz substrate coated with PIM-1 solution and heated in high temperature. Without any additional process, organic solar cell can be made directly on the sheet to manufacture solar cells. (b), (c), (d) show thickness, surface resistivity and transparency of the carbon nanosheet, respectively in relation to the concentration of PIM-1. Source: KIST
A polymer was synthesised with a rigid ladder structure, namely PIM-1 (polymer of intrinsic microporosity-1). The quartz substrate was spin-coated with the PIM-1 solution before it was heat-treated at 1,200°C—resulting in a transparent and conductive carbon nanosheet.
In recognition of the innovative approach, the research was introduced on the cover of Nanoscale, a high impacting peer-reviewed journal in the field of nanoscience. The team was led by Dr. Han-Ik Joh at KIST, along with Dr. Seok-In Na at Chonbuk National University and Dr. Byoung Gak Kim at Korean Research Institute of Chemical Technology.
Figure 2: Image of the resulting transparent carbon nanosheet (15mm). Source: KIST
The carbon nanosheet can be mass-produced in a simpler process while having high quality since the new process bypasses the steps that are prone to formation of defects such as elimination of the metal substrate or transfer of graphene to another board. The final product is as effective as graphene.
Dr. Han Ik Joh at KIST said, "It is expected to be applied for commercialisation of transparent and conductive 2D carbon materials without difficulty since this process is based on the continuous and mass-produced process of carbon fibre."
This is a follow-up research from the team that recently released its findings on the carbon nanosheet manufacturing based on polyacrylonitrile (published in the 2013 Carbon Vol. 55 and Applied Physics Letters Vol. 102). The new findings are even more meaningful as it offers deeper understanding on the growth mechanism of carbon nanosheet and much simpler manufacturing process.
The research was conducted with the funding from the KIST Proprietary Research Project and National Research Foundation of Korea.
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