Organic light-emitting diodes (OLEDs) significantly impact daily life, according to Professor Chi Yun, Chair Professor in the Department of Materials Science and Engineering and Department of Chemistry at City University of Hong Kong (CityU).

They dominate the market for flat-panel displays for both hand-held electronics and larger screen TVs due to their low power consumption, high definition, and versatile form factors. Now only two kinds of emitters in this highly specialised field require further exploration: true-blue and near infrared (NIR) emitters.

In this latest talk in the President’s Lecture Series: Excellence in Academia, held online on 23 March and titled “Transition-metal phosphors and corresponding organic light emitting diodes”, Professor Chi talked about the effect of these two emitters on the development of related transition-metal based phosphors and OLED devices.

The content of the talk served as an overview of Professor Chi’s current research interests on the photophysical and opto-electrical properties of organic and organometallic materials, and the design of transition-metal phosphors for OLEDs.

He began his talk by describing the advantages of OLED devices, ranging from low driving voltage, all the way, to low costs. “As a result, OLED has been successfully employed in making display for cellphones, TV sets, foldable displays, luminaries for indoor lighting, and devices for virtual reality,” he said.

He then noted that the commercial architecture of OLED displays and emitters was important for displays on electronic devices.

In particular blue phosphors, i.e. a substance that exhibits the phenomenon of luminescence, from light blue to deep blue, can significantly reduce power consumption, which is very important for cellphones, as the majority of electrical energy is consumed by display.

Referring to NIR emitters, he described their applications for monitoring the human pulse and oxygen levels in blood, boosting immunity, balancing hormones and rejuvenating the skin, and for use in sports bracelets.

In particular for healthcare, devices fabricated using NIR OLEDs “provide a 2D image of oxygen distribution, essential for monitoring wound-healing processes of patients,” Professor Chi said. “It is notable that only OLED can provide the high resolution needed for this class of applications.”

Professor Chi concluded on a positive note for transition metal phosphors and OLEDs. “The prospects of transition-metal OLED phosphors remain promising, particularly, in the design and preparation of efficient and durable phosphorescent OLEDs, both true-blue and NIR,” he said.