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Gaining Clarity on Transparent Conductive Electrodes

Gaining Clarity on Transparent Conductive Electrodes

Electronics are complicated products. When you stop to really think about it and itemize the components of your flat screen TV, tablet, and even LED light bulb, there is much more than circuitry, wiring, and glass contained inside. There is, in fact, a significant opportunity for materials innovation as manufacturers seek to provide products that are lighter, faster, and more energy efficient. My colleague Andrew has previously blogged about LED lighting innovation in relation to increasing energy efficiency, and here I will focus on transparent conductive electrodes (TCEs), which are used in touch panels, flat displays, photovoltaics, lighting, and more.

Transparent electrodes are getting a lot of attention these days. The incumbent technology, Indium Tin Oxide (ITO), uses indium, an expensive metal that is subject to commodity volatility. The Chinese government controls the vast majority of the global supply and has placed restrictions on the production of indium further increasing costs. If you’ve ever questioned why your smartphone has a sticker price of over $500 – you can blame ITO in part as it can account for up to 40% of touch screen production costs.

A second driver for innovation in the transparent electrode space is the advent of flexible displays. While this market is small today, it is growing extremely rapidly. ITO is not an ideal material for flexible displays due to its brittleness, performance and manufacturability. The flexible display market is predicted to increase more than 4 times in 2014 with sales approaching $100 million (IHS). The rapid growth of this market contributes to an extremely large transparent electrode market of $5 billion by 2020! Furthermore, non-ITO transparent electrodes are expected to make up approximately 34% of the market by 2017.

As this market appears primed for take-off, and the hockey stick growth curves we so like to see in the VC world, what are the emerging materials that might replace ITO in the aforementioned applications?

Well, there are 6 main contenders that will have to battle it out. In no particular order they are silver nanowires, carbon nanotubes (CNTs), metal mesh, graphene, conductive polymers, and other transparent conductive oxides (TCOs), which are largely doped zinc oxides. First, to point out the obvious – CNTs and graphene are both carbon-based, attractive candidates due to their mechanical and conductive properties, and represent an active area of research and development. Arguably, CNTs (both the single-walled and double-walled varieties) are further along the commercialization path, though perhaps not necessarily for this application, while graphene continues to experience slow growth as cost and manufacturability remain challenging.

Silver nanowires have also made it out of the lab and are being commercialized by a few start-up (and more established) ventures. While the time to market has been lengthy, I think it’s reasonable that we will see silver nanowires in commercially available touch displays and OLED lighting panels soon as there are some well funded companies with industry partnerships in the works.

Transparent conductive oxides are an interesting group of materials. It is rare for a bulk material to offer both high electrical conductivity and high visual light transmission. Many of these are doped zinc oxides which may have some challenges with stability and difficult to handle precursors in the manufacturing process. Additionally, some TCOs may lack the flexibility characteristics now demanded by OEMs and must perform as well as, if not better than, ITO. Depending on the application and performance requirements, fluorine tin oxide (FTO) – a readily available close cousin of ITO may do. A competing class of material is transparent conductive polymers as they have also found there way into commercially available devices. Conductive polymers are interesting because they can be made into flexible films, however they are less conductive than the aforementioned transparent conductive oxides.

And last but not least, metal mesh is perhaps the most likely material to gain traction in the ITO replacement market. Metal mesh may have the most compelling costs and also meets the performance requirements for flexible display and organic electronics applications. Metal mesh may be able to take advantage of innovations in the printed electronics space for easier manufacturing however issues with visibility of the metal mesh and interference with the display microstructure still must be resolved.

To date, ITO replacements have gained limited traction in the consumer electronics market. However, the applications of these emerging materials have been limited to touch panels with small screens such as smartphones and tablets. The key challenge (aside from demonstrating manufacturability at scale and at an appropriate cost) is performance. As devices get larger, and the touch display industry moves from smartphone and tablets to all-in-one PCs, the resistance (performance) of the transparent electrode becomes more important. Successful innovations in this arena will have to demonstrate manufacturability at scale. Moreover, support of OEMs through development partnerships will be necessary to not only gauge performance and cost impacts, but to also validate industry support and provide assurances of inclusion in new products.

We have written a few blogs that highlight the importance of partnerships and strategic relationships for start up companies and the electronics market is no different. By partnering with OEMs or other strategics – which include some companies Pangaea’s limited partner network – innovators in the TCE market are able to benefit from the manufacturing and scale up expertise that they bring to the table. With this market primed to explode, Pangaea continues to keep an eye on innovations which improve performance and increase efficiency and have an opportunity to take a part of this dynamic market.

Associate, Pangaea Ventures Ltd. Sarah is an environmental scientist and MBA who has been active in sustainability efforts for York and Dalhousie universities, as well as the City of Toronto's Environment Office.View Sarah Applebaum's profile on LinkedIn

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Guest Tuesday, 19 November 2019