A Promising New Material in Terms of Cost and Yield for OLEDs
Researchers at the Paul Scherrer Institute (PSI) have gained insights into a promising new material for organic light-emitting diodes (OLEDs).
Many of the materials that engineers have been considering for use in OLEDs contain expensive additives like iridium. This makes their large-scale use impractical due to cost constraints. However, researchers at PSI have discovered a new green luminescent substance that could enable OLEDs to deliver higher light yields on a large scale without incurring any additional costs.
In their research study, the authors describe how the research team turned to the copper-containing compound CuPCP which can be easily produced in large quantities and gives off an intense green glow when current is applied and also when it is under UV light.
The researchers investigated the short-lived excited states of CuPCP and examined how the compound was able to change when it absorbed energy, and how the charge was distributed over individual atoms when excited. “We wanted to understand what the excited state of the compound looks like,” physicist Grigory Smolentsev said. “This reveals how high the losses of energy that will not be released as light are likely to be, and it shows us how we can possibly minimize these losses.”
The CuPCP compound is a yellowish solid and when it is dissolved in liquid, or when a current is applied, it gives off an intense green glow. This is caused by the molecules absorbing the energy supplied to them and gradually emitting it again in the form of light—a process known as electroluminescence upon which LED principles are based.
The CuPCP compound glowing in vials under UV light. Image used courtesy of the University of Bremen
Rapid Development of New Lighting Appliances
Through their measurements, the researchers were able to confirm that the CuPCP compound could potentially be used as a light-emitter for OLEDs. In fact, the researchers claim that CuPCP is a “hot candidate” for producing OLEDs due to its chemical structure.
According to the research study, this is because the compound’s properties make it possible to achieve a high light yield. One reason for this is that the molecule’s 3D structure is relatively stiff and only changes by a marginal amount when it becomes excited.
In addition to investigating CuPCP as an OLED candidate, the experimental data obtained by the researchers could help improve theoretical calculations about the suitability of other molecules as OLED light emitters. So in the future, it will be possible to better predict, "Which compounds are more suitable for OLEDs and which less." Smolentsev said. “The measurement data will help the chemists understand which part of the molecule stands in the way of high efficiency. And of course, how the compound can be improved to increase its light output.”
Potential Applications for Consumer Devices
Potential applications for this “promising” new material include consumer devices like smartphones and television screens. These have already benefitted from the use of OLEDs for a few years now, with the first flexible television screens that use them having only recently come to market.
If this material is all that it is reported to be, manufacturers and designers could find themselves benefitting from a more stable, higher energy candidate that is cheaper to source, which could be a boon for the development of the next generation of OLED screens.