The manufacture of displays has always been an energy-intensive endeavour, and one of the key reasons for this is the production of transistors over large areas. Whether the display be LCD or OLED, transistors are needed behind each and every one of the millions of pixels across the display.
Most commonly, these transistors are made of silicon, on a glass substrate, and require temperatures during manufacture of up to 450°C or more, depending on the type. Furthermore, the deposition of the transistor materials themselves (silicon and dielectrics) involve the use of very energy-intensive, high temperature and vacuum processes, such as Chemical Vapour Deposition (CVD), ion implantation and sputtering. This applies whether the display is built on glass (LCD, OLED) or, more recently, thin flexible polyimide (e.g. flex OLED), because they both use silicon transistors.
The total energy consumption is exacerbated by the sheer area of display production needed globally every year. Unlike microchips, which provide their functionality in the smallest chip size possible, displays require large areas, and the average display size is growing year on year.
Today’s global display capacity is over 300 million m2 per year, with the latest and largest ‘Gen 10.5’ display factories each capable of producing 10 million m2 annually. Such a colossal factory can consume energy in the range of 100 megawatts – the equivalent of a small power station.
This energy consumption doesn’t include the energy involved in making the input materials, which can be very energy intensive in their own right. Take glass for example, which forms the substrate for the vast majority of displays. Glass production is one of the biggest consumers of energy across all industries: to create a single kilogram of glass requires around ten million of Joules of energy.
The displays industry today requires around 600 million m2 of glass per year (2 sheets per display) – that’s around 2,000 tonnes per day! This mountain of glass ends up incorporated into the finished displays, accounting for 90% of a display’s mass excluding the backlight. It is then shipped all over the world with additional energy consumption.
Globally, as we face up to the environmental impact of humanity on our planet, more energy (of the human sort) is going towards finding alternatives approaches to manufacturing, ideally those which both advance product performance and reduce environmental impact.
Flexible organic electronics is an example of a disruptive technology that brings both game-changing flexibility to an industry – in this case displays – whilst significantly reducing the energy footprint in manufacturing compared to glass displays.
For example, Organic LCDs or OLCD are displays that can be manufactured on plastic films instead of glass, made possible by a new class of organic semiconductor materials that are processed at much lower temperatures compared to the silicon that they replace.
Organic transistors can replace silicon in existing display fabs, allowing displays manufacturing at temperatures never exceeding 100°C – bringing major production energy savings whilst allowing manufacture on plastic films instead of glass. The resulting displays can be wrapped around almost any surface, addressing a $100bn market that needs flexible conformable displays and optics for active surfaces in consumer, wearables, AR, VR, automotive and signage.
‘Reduce, reuse, recycle’ is a phrase that originally came to prominence in the 1970s but has made a comeback in recent years as we assess and address our impact to the planet. FlexEnable’s Organic LCD and Optics directly advance manufacturing sustainability across all three:
Reduce – At 100°C, the reduced temperature of organic semiconductors compared to 300°C-500°C of silicon reduces energy consumption in production compared to glass displays, because of the much lower temperature and simpler process that avoids energy-intensive processes such as CVD and ion implantation. The combined energy savings reduce production energy by around 25%. With a medium-sized (Gen 6) display factory consuming around 500 GWh/year, this is a major energy saving.
Reuse – OLCD is purposefully designed to re-use existing factories originally built to make glass displays. This prolongs the useful economic life of existing installations by giving them the capability to manufacture highly disruptive flexible display technology and then rapidly scale volume production.
Recycle – The low process temperatures allow a plastic film known as TAC (Tri acetyl cellulose) to be used as the substrate instead of glass. TAC is a widely available bioplastic made of a cellulose derived from the same raw material as paper, is highly recyclable and biodegradable, and already used in the displays supply chain. During production of the flexible displays, the TAC film is stuck to a sheet of display glass. After production is complete the flexible display is removed and the glass is reused for the next display.
If these energy savings were applied industry-wide to all display fabs it could save around 10 TWh/year energy saving per year – enough to power 1 million homes – and 5 million tonnes of CO2.
Flexible displays redefine where and how we can bring surfaces to life, and low temperature – meaning low energy – manufacturing that’s made possible by organic electronics, results in flexible displays that are easier and cheaper to make, while reducing the environmental impact. All manufacturing processes have an environmental impact, and they key is to minimise it without stifling the advancements to technology and product innovation.
About the author
Dr Paul Cain is Strategy Director at FlexEnable. He has 20 years’ experience in the flexible electronics and displays industries, in both technical and strategic management roles. He has taken new flexible display technologies from lab to fab to commercial product and has 25 patents relating to processes and architectures that enable the high-yield manufacture of flexible displays. Cain has a PhD in physics from the University of Cambridge, UK, and an MBA from London Business School.