Organic light-emitting diodes demonstrate high luminosity at lower voltages

A team of researchers from organic photovoltaic cell development company Nextgen Nano has discovered a means of producing organic light-emitting diodes (OLEDs) that demonstrate high luminosity at lower voltages.

The findings, published in Nature Communications, will lay the groundwork for efficient high-performance OLED devices in the future and may change future approaches to organic semiconductor technology.

The research, led by Nextgen Nano’s New Fusion division at the NCSU laboratory, found that certain organic molecules were able to achieve electroluminescence at lower driving voltages than is typically required by current OLEDs.

These molecules exhibited fluorescent properties at lower energy values, allowing them to illuminate at notably lower voltages than phosphorescent OLEDs and to produce a stable blue OLED with a higher operating power efficiency compared to existing blue phosphorescent OLEDs.

This research means that it is possible for display applications in the future to provide superior levels of luminosity while using half the energy, which will also extend the operational life of the device.

The study found that the tested blue OLED produced 1000 candela per square metre at 3.4 volts, which was less than 50% of the voltage required by other tested blue OLEDs.

The research was headed up by Felix N Castellano, of North Carolina State University’s (NCSU) Department of Chemistry, and Franky So, of NCSU’s Department of Materials Science and Engineering.

Prof So is also chief technology officer (CTO) of Nextgen Nano and has worked with OLED technology extensively in the past, having previously serving as head of Motorola’s OLED research group.

“With this research, we’ve found a way to overcome the traditional energy limitations of OLED technology,” explained Prof Castellano. “By choosing organic material with the right molecular properties, we can achieve electroluminescence at voltages below the molecule’s bandgap voltage. This results in significantly lower power consumption for devices, without sacrificing the stability or luminosity of the display.

“If these OLEDs were used in a smartphone display, the brightness of the screen would draw less power from the battery. Not only would this extend the phone’s battery life, we expect that this lower operational power could also maximise the operational lifespan of the OLED, but we will conduct further experiments to confirm this.”

In addition to research into OLED technology, New Fusion has been actively researching the development of organic photovoltaic (PV) cells that can be used in the next generation of solar technology. This technology is being developed with NextGen Nano, with the aim to produce low-cost, high efficiency PV technology that is flexible and sustainable.

“The current challenge in the OLED technology is blue,” according to Professor So. “Our finding shows that it is possible for make a fluorescent OLED with half of the voltage required for phosphorescent OLEDs. And that can significantly improve the device operating lifetime.”

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