Graphene was first isolated in 2004, but its commercialization only began in earnest in the last 5 years. It has remarkable electronic properties, with an extraordinarily high charge carrier mobility and conductivity. It is an excellent conductor, and transports electrons tens of times faster than silicon opening up the possibility of a sizeable graphene electronics market. These properties make it an ideal candidate for next generation electronic applications such as transistors, batteries, ultracapacitors and sensors.
However, the absence of band-gap limits its usage for some purposes, like digital switching, where a high value of the on-off current ratio is an essential requirement. Fortunately, this limitation can be overcome by inducing quantum confinement and edge effects as in the case of narrow width graphene nanoribbons (GNRs) with controllable widths and smooth edges.
Graphene electronics market
Near-term electronics applications for graphene are in radio-frequency identification (RFID) tags, low-resolution displays and backlights, sensors, electrical contacts, analog signal processing and electronics packaging. Graphene-based conducting inks are finding their way into smart cards and RFID tags. Chinese companies are expecting to bring graphene products to the market in 2014 in consumer electronics arena.
The development of future flexible and transparent electronics relies on novel materials, which are mechanically flexible, lightweight and low-cost, in addition to being electrically conductive and optically transparent. The demand for transparent conductors is expected to grow rapidly as electronic devices, such as touch screens, displays, solid state lighting and photovoltaics become ubiquitous in our lives. Graphene is being developed as a potential replacement for indium tin oxide (ITO) in touchscreens, which is the dominant transparent conductor in the electronics market. ITO is expensive, there are difficulties in the fabrication steps and it is becoming increasingly scarce as global indium supply dwindles. ITO is also mechanically rigid, making it unsuitable for future flexible electronics applications. As a result, non-ITO transparent conductors such as graphene are coming increasingly to the fore. Applications for transparent conductors include touch sensors, displays, lighting, thin-film solar (PV), smart windows, and EMI shielding. There are around 200 companies and research institutions currently developing ITO alternatives such as metal meshes, silver nanowires, conductive polymers, carbon nanotubes, other 2-D materials and GaN.
|
Table1: Properties of materials for transparent conducting film (Y. Lee & J.-H Ahn) |
|
Thickness (nm) |
Transparency (%) |
Sheet resistance (Ω/sq) |
Failure strain (%) |
Cost
|
|
| ITO | 100~200 | >90 | 10~25 | 1.4 | 120 $/m2 |
| PEDOT: PSS | 15~33 | 80~88 | 65~176 | 3~5 | 2.3 $/ml |
| Silver nanowires | ~160 | 92 | 100 | ~1.2 | 40 $/m2 |
| CNT | 7 | 90 | 500 | ~11 | 35 $/m2 |
| Graphene | 0.34 | 90 | ~35 | ~7 | 45 $/m2 |
However, graphene is at the forefront of this growing market. A network of graphene nanostructures provides an inexpensive alternative to ITO, and is also flexible and stretchable. Graphene oxide films can be deposited on virtually any substrate, and later converted into a conductor. Therefore it is expected that transparent graphene films may replace rigid and brittle ITO films in touch panel screen electrodes.
Commercialisation
Samsung is the main technology developer in graphene transparent conductors and there are a number of producers, application developers and OEMS working in the area.
Image 1: Graphene smart phone prototype (Samsung).
Chinese company Chongqing Morsh Technology is building a production facility in Chongqing that they claim will be used to produce 15” single-layer graphene films. They are planning start production by March 2014, and they have already signed an commercial agreement with Guangdong Zhengyang, an OGS maker to produce 10 million graphene based transparent conducting films (TCFs) in a year for the next five years, for application in touchscreens.
Vorbeck Materials (http://vorbeck.com) and BASF (www.basf.com) are developing dispersions of highly conductive graphene for producing electrically conductive coating and compounds especially for the electronics industry. Other companies active in this sphere include Graphene Frontiers (www.graphenefrontier.com),
Graphenea (www.graphenea.com)and Graphene Devices (www.graphenedev.com). Graphene Frontiers is developing methods to produce large area graphene on an industrial scale.
Image 2: Graphenea conductive film (Graphenea).
According to Graphene Frontiers, they have solved the problems of scale: CVD Graphene films can now be mass-produced and transferred to nearly any substrate. The company claim their patent pending method for low cost production and etch-free transfer of graphene films will disrupt multi-billion dollar markets including sensors, energy storage, and flexible electronics. The company’s GF-3012 product is transparent conductive film loaded on transparent glass slides for ITO replacement. Most graphene producers are aiming for the electronics industry as the key market.
UK-based graphene producer Haydale (www.haydale.com)is producing conductive inks in collaboration with Gwent Electronic Materials for application in flexible electronics.
Bluestone Global Tech (http://bluestonegt.com) is producing Grat-FilmTM for application in touch panels and LEDs. Chinese company Powerbooster Technology is utilizing the film in graphene-based flexible touch-panels for mobile devices. The company has stated that it plans to invest $150 million over three years to incorporate graphene into mobile devices.
Image 3: Powerbooster’s flexible touch panel prototype.
Graphene Laboratories, Inc., sells graphene conductive films via the Graphene Supermarket (www.graphene-supermarket.com). Sony is also at the forefront of production. In 2013 it announced fabrication of high-quality 100m long graphene transparent conductive film with a sheet resistance as low as 150 Ω/sq.
However, large scale production of low sheet resistance and high optical transparency graphene films that are electrically stable over time has yet to be fully established.
The scalability, reproducibility and cost effectiveness of integrating them into practical devices is currently under development. Also, graphene ‘s success in transparent conductors is also dependent on the development of competing alternative materials, such as thin metal films, metal nanowire films, conducting polymers and various other forms of hybrid films, as well as other 2D nanomaterials that are coming to prominence.
Further information on graphene in electronics: Graphene: The Global Market to 2020, Future Markets, Inc., www.futuremarketsinc.com/index.php?option=com_content&view=article&id=113:the-world-market-for-graphene&catid=1:all-reports&Itemid=59. Main article image courtesy of Graphene Frontiers.
