Feature: LEDs
One of the biggest selling points for OLEDs is their ability to render true black, which means they can produce higher contrast images
counterparts. In a display, this means that colour balances shiſt as the blue OLEDs lose luminosity faster. While the device itself may still be functional, the quality and colour of the picture will be diminished. Because of this issue, companies have
been reluctant to use OLEDs in their displays, despite their superior true black potential and wider viewing angles. What’s more, while red and green OLEDs have longer operational lifespans compared to blue OLEDs, they still deteriorate faster than LEDs. A more efficient and durable OLED is sought by design engineers and manufacturers. In response to these challenges,
recent research has identified a new generation of OLED. Published in Nature Communications in 2019, NextGen Nano’s New Fusion division found that certain organic semiconductors achieved fluorescence at lower energy values than for OLEDs used today. Te study found that the OLEDs produced 1,000 candela per square metre at 3.4V – approximately 50% of the voltage required by current OLEDs. By choosing organic materials with
the right molecular properties, the team achieved electroluminescence at voltages below the molecule’s bandgap voltage. Tis resulted in an OLED device working at a significantly lower power consumption, without sacrificing stability or luminosity. Although the new technology exhibits a lower internal quantum efficiency than conventional OLEDs, the lower operating voltage earns this efficiency back. Electroluminescence at voltages lower than the semiconductor’s bandgap means
Times Square billboards use 161 megawatts annually at the cost of some $10m
OLEDs in displays would draw less energy to emit light. In turn, better power efficiencies like these bring lower energy losses. Because the organic molecules of blue OLEDs are particularly susceptible to degradation, lower operating voltages will directly extend the life of the blue OLED and the overall device.
Reinventing the display Exciting organic semiconductor materials too much causes quick degradation, particularly for blue OLEDs. Tis is why for displays built to last many years, high operating voltages are undesirable. It would be costly and laborious to replace
the display every few years when its output falls to unacceptable levels. Terefore, the research conducted on OLEDs not only underlines the potential of using less energy to generate brighter displays, but also it highlights how they can operate for longer without deteriorating. OLED technology continues to be the
focus of high-tech companies. With further improvements it may become possible to replace high-powered displays like those in Times Square with technology drawing less energy from the grid, energy bills could reduce dramatically. It’s only a matter of time before the true potential of OLED technology is properly recognised.
www.electronicsworld.co.uk April 2021 27
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