Search Menu
Photonics Media Photonics Buyers' Guide Photonics EDU Photonics Spectra BioPhotonics EuroPhotonics Industrial Photonics Photonics Showcase Photonics ProdSpec Photonics Handbook
More News
Email Facebook Twitter Google+ LinkedIn Comments

Researchers Demonstrate Efficiency of Radical-Based OLEDs
Nov 2018
CAMBRIDGE, England, Nov. 27, 2018 — Radicals — semiconducting molecules with unpaired electrons — can be used to fabricate highly efficient OLEDs, according to scientists at the University of Cambridge and Jilin University. Using a luminescent radical emitter, the researchers demonstrated an OLED with maximum external quantum efficiency of 27 percent, at a wavelength of 710 nm. According to the team, this is the highest reported value thus far for deep-red and IR LEDs.

The emission process of the radical-based OLEDs originates from a spin doublet, rather than a singlet or triplet exciton. Stabilized radicals form electronic states (known as doublets), on account of the spin character being either up or down. The efficiency limitations imposed by triplet excitons are circumvented for doublets. The researchers exploited this spin property to overcome efficiency limitations such as those found in traditional OLEDs.

When isolated in a host matrix and excited with a laser, the radicals showed near-unity efficiency for light emission. The electrical current injected electrons into the unpaired electron energy level of the radical, and pulled electrons out of a lower-lying level to form bright-doublet excited states.

This highly emissive behavior was translated to highly emissive LEDs. “The radicals themselves are unusually emissive, and they operate in the OLEDs with unusual physics,” said researcher Emrys Evans.

For traditional compounds (i.e., nonradicals without an unpaired electron), quantum-mechanical-spin considerations dictated that charge injection will form 25 percent bright-singlet and 75 percent dark-triplet states in OLED operation. The researchers believe that radicals could offer a solution to this fundamental spin problem in OLEDs.

The researchers are investigating ways to exploit radicals beyond lighting applications, and they expect radicals to affect other branches of organic electronics research. With further materials research, efficient blue- and green-light radical-based diodes could be developed, the researchers said, forming the basis for next-generation displays and lighting technologies.

The research was published in Nature (

Research & TechnologyeducationUniversity of CambridgeLEDsOLEDsOrganic light-emitting diodeslight sourcesradicalsradical-based OLEDsmaterialsDisplayslighting design

Terms & Conditions Privacy Policy About Us Contact Us
back to top
Facebook Twitter Instagram LinkedIn YouTube RSS
©2018 Photonics Media, 100 West St., Pittsfield, MA, 01201 USA,

Photonics Media, Laurin Publishing
x We deliver – right to your inbox. Subscribe FREE to our newsletters.
We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.