Transistors, the tiny electronic switches that power modern electronic devices, have changed significantly over the past few decades. But their manufacturing process has traditionally been energy-intensive and as such has a considerable environmental impact. FlexEnable’s recent breakthrough in organic thin-film transistor (OTFT) manufacturing offers a more sustainable approach.
The transistors, made from organic semiconductors, are produced using a solution-based low-temperature process that is far more energy efficient than traditional methods. The technology has been industrialised by FlexEnable and entered mass production for the first time in June 2024 in a consumer device.
The inherent flexibility of OTFT technology opens up exciting possibilities for new product designs and improved features, while also being kinder to the planet.
How does FlexEnable OTFT process save energy?
Our approach enables the manufacture of OTFTs at temperatures under 100°C for each and every process step used in their manufacture. Not only does this low temperature allow the OTFTs to be built onto flexible bioplastic substrates instead of glass, but also results in a major energy saving – around half the energy is saved in the TFT production by switching from silicon to organic.
In comparison, silicon and other inorganic transistors necessitate high temperature processes – even “low” temperature polysilicon (LTPS) requires 450°C+ processes. Each transistor device substrate will require many high temperature cycles during manufacture resulting in a significant energy consumption. A large display fab can consume hundreds of GWh per year.
FlexEnable’s manufacturing process involves attaching a low-cost plastic film to a reusable glass carrier and then use our low-temperature process and FlexiOM materials to manufacture flexible organic transistors on the plastic film without the need for energy-intensive steps such as high temperature annealing and curing, chemical vapour deposition (CVD) or ion implantation.
At the end of the process, the plastic film is removed from the glass, and the glass can then be reused for the next production run. All of the process steps from laminating the substrate to removing the substrate, are undertaken at less than 100°C. This is a uniquely low temperature for active electronics production.
Reduce, reuse and recycle
FlexEnable’s low-temperature manufacturing method for organic transistors significantly reduces energy consumption compared to silicon transistors by implementing the three Rs (normally associated with waste management):
Reduce: A significant reduction in manufacturing energy consumption
Combined with the removal of energy intensive steps like CVD and ion sputtering, this can provide up to 50% reduction in direct production energy for a manufacturing the transistors compared to silicon.
Reuse: Reusable glass carrier, no glass consumption
Glass is used only as a carrier and can then be reused for the next batch or recycled. As glass production itself is one of the biggest consumers of energy across all industries (around 13 MJ/kg), and a typical display factory can consume up to 10 million m2 of glass in a single year – removing the glass consumption provides for a reduction in overall energy usage.
Moreover, the OTFTs are manufactured in the same flat panel display factories that use current methods and equipment – so there’s no need to build a new factory to access the advantages. There are many factories with underutilised equipment that could be repurposed prolonging their useful life.
Recycle: Bioplastic substrates
Due to the low process temperatures, plastic films can be used instead of glass. One example of this which we most commonly use is Tri-acetyl Cellulose (TAC), a widely available bioplastic made of a cellulose derived from the same raw material as paper. TAC has excellent optical properties so is ideal for displays. It is biodegradable and has been in use in the display supply chain for many years.
OTFT is in production today
In June 2024 we announced that these organic transistors are in mass production and are now shipping in the world’s first mass-produced consumer product with an OTFT display – a crypto wallet device, called Ledger Stax.
Ledger Stax features the world’s first mass-produced OTFT display. Image credit: Ledger
FlexEnable’s process is a method for manufacturing flexible organic transistors that can be used in flexible displays and ultra-thin, light dimming films for AR glasses. These flexible displays are needed for new consumer electronics applications for which silicon-based displays cannot meet the design or performance requirements. Our approach not only enables greater design freedom but brings the additional benefits of being more energy efficient during production and therefore more sustainable.
We are proud to be a finalist in the Sustainability category at the IET Excellence and Innovation Awards 2024.
