Nav: Home

New mechanism allows lower energy requirement for OLED displays

June 05, 2019

Scientists from RIKEN and the University of California San Diego, in collaboration with international partners have found a way to significantly reduce the amount of energy required by organic light emitting diodes (OLEDs). OLEDs have attracted attention as potential replacements for liquid crystal diodes, since they offer advantages such as being flexible, thin, and not requiring backlighting.

The group achieved the advance, published in Nature, by developing a new way to manipulate the "excitons"--pairs of electrons and holes--that are key to the transport of electrons within OLEDs. Essentially, current passing through the device creates such pairs, and when they change to a lower energy level, and emit visible light in the process. Normally, the excitons in OLEDs arise in two patterns, with the spins being either the same or opposite, and the ones with same spins--known technically as triplet excitons--are three times more common. However, the singlets, which are created along with the triplets, require more energy, and though they can be converted into triplets it still means that the device as a whole requires the energy to create them in the first place.

In the current work, the group found a way to lower the voltage so that only triplets are formed. The work began with fundamental research to understand the basic physics behind the creation of excitons using precise single-molecule electroluminescence measurements using a scanning tunneling microscope (STM) combined with an optical detection system. They prepared a model system based on an isolated molecule of 3, 4, 9, 10-perylenetetracarboxylicdianhydride (PTCDA), an organic semiconductor, adsorbed on a metal-supported ultrathin insulating film. They used a special technique to impart a negative charge to the molecule. Then, they used the current from an STM (scanning tunneling microscope) to induce luminescence in the molecule, and monitored what type of exciton was created based on the emission spectrum. The measurements showed that at low voltage, only triplets were formed. Theoretical calculations by Kuniyuki Miwa and Michael Galperin at UC San Diego confirmed the experimental results and substantiated the mechanism.

"We believe," says Kensuke Kimura of the RIKEN Cluster for Pioneering Research, "that we were able to do this thanks to a previously unknown mechanism, where electrons are selectively removed from the charged molecule depending on their spin state."

"It was very exciting to discover this new mechanism," says Yousoo Kim, leader of the Surface and Interface Science Laboratory in the RIKEN CPR, "We believe that these findings could become a general working principle for novel OLEDs with low operating voltage."
-end-
The work was done by researchers from RIKEN, the University of California San Diego, the University of Tokyo, and the Institute for Molecular Science.

RIKEN

Related Electrons Articles:

Using light to put a twist on electrons
Method with polarized light can create and measure nonsymmetrical states in a layered material.
What if we could teach photons to behave like electrons?
The researchers tricked photons - which are intrinsically non-magnetic - into behaving like charged electrons.
Electrons in rapid motion
Researchers observe quantum interferences in real-time using a new extreme ultra-violet light spectroscopy technique.
Taming electrons with bacteria parts
In a new study, scientists at the MSU-DOE Plant Research Laboratory report a new synthetic system that could guide electron transfer over long distances.
Hot electrons harvested without tricks
Semiconductors convert energy from photons into an electron current. However, some photons carry too much energy for the material to absorb.
Cooling nanotube resonators with electrons
In a study in Nature Physics, ICFO researchers report on a technique that uses electron transport to cool a nanomechanical resonator near the quantum regime.
New method for detecting quantum states of electrons
Researchers in the Quantum Dynamics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) devised a new method -- called image charge detection -- to detect electrons' transitions to quantum states.
Slow electrons to combat cancer
Slow electons can be used to destroy cancer cells - but how exactly this happens has not been well understood.
How light steers electrons in metals
Researchers in the Department of Physics of ETH Zurich have measured how electrons in so-called transition metals get redistributed within a fraction of an optical oscillation cycle.
Twisting whirlpools of electrons
Using a novel approach, EPFL physicists have been able to create ultrafast electron vortex beams, with significant implications for fundamental physics, quantum computing, future data-storage and even certain medical treatments.
More Electrons News and Electrons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Uncharted
There's so much we've yet to explore–from outer space to the deep ocean to our own brains. This hour, Manoush goes on a journey through those uncharted places, led by TED Science Curator David Biello.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Dispatch 2: Every Day is Ignaz Semmelweis Day
It began with a tweet: "EVERY DAY IS IGNAZ SEMMELWEIS DAY." Carl Zimmer – tweet author, acclaimed science writer and friend of the show – tells the story of a mysterious, deadly illness that struck 19th century Vienna, and the ill-fated hero who uncovered its cure ... and gave us our best weapon (so far) against the current global pandemic. This episode was reported and produced with help from Bethel Habte and Latif Nasser. Support Radiolab today at Radiolab.org/donate.