Producing Flexible and Recyclable Optoelectronics Through ‘Cheaper’ Electrodes

June 18, 2020 by Luke James

Researchers in Australia have demonstrated the potential for a new type of flexible, recyclable electrode that could be used to create cheaper optoelectronics such as touchscreens, solar cells, and wearable “e-skins”, they claim.

Indium tin oxide (ITO) is widely used in electronics. From laptop and touchscreen displays to thin-film solar cells, this ubiquitous material makes possible many of the technologies that we now take for granted. However, with indium becoming more and more scarce, ITO’s price is quickly rising and this is jacking up the price of the components that use it, making them more expensive to produce. In addition to the rising price tag, ITO is also very fragile, and this limits its applications. 

Now, Australian researchers at the ARC Centre of Excellence in Exciton Science may have found a new type of electrode that is both cheap and flexible, in theory making it a perfect replacement for ITO. 


Nanosphere Lithography

Dr. Eser Akinoglu, a contributing author at the ARC Centre, said: “The performance of the material is excellent, the transmission of above 90% and high electrical conductivity rivals the ITO benchmark." Speaking of the potential commercial applications for the team’s research, he commented that, in theory, it could be integrated into industrial roll-to-roll printing—the process of creating electronic devices on a roll of flexible foil—paving the way for cost-effective wearable technology and truly flexible screens. 


Nanomesh on PET substrate as a transparent and flexible circuit lighting up a blue LED.

Nanomesh on PET substrate as a kangaroo-patterned transparent and flexible circuit lighting up a blue LED. Image credited to Dr. Tengfei Qiu


The dielectric/metal/dielectric (D/M/D) nanomesh electrodes are produced using nanosphere lithography, a simple and cost-effective deposition method which involves evaporating the desired combination of materials into a nanoscale pattern. Thanks to this method, the electrodes were found to exhibit precisely controlled perforation size, wire width, and uniform hole distribution. This yielded high transmittance, low sheet resistance (minimizing voltage losses), and flexural endurance. 


A Possible Sustainable Alternative

Additionally, in certain applications, the electrodes can even be recycled, making them more sustainable and a potential alternative to more established manufacturing materials and processes. Speaking about the electrode’s recyclability, Dr. Akinoglu said: "It means that if you make a device like an electrochromic window, which may deteriorate in functionality after its life-span, you can take it apart, flush rinse the electrodes, and reuse them for another device."

Next, the researchers want to explore the potential demonstrated in this study to create similar results at scale with a long-term view of achieving similar results while also showing commercial viability. "You want to get the transparency higher, you want to get sheet resistance lower and you want to get the endurance for mechanical stress and flexibility higher," Dr. Akinoglu said. "And you want to be able to fabricate it on a large-scale area, at a low cost."

If the team is able to do this, they may well provide a viable platform for the development of next-generation, environmentally-friendly optoelectronics.