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Research Achievements
A team led by SNU Professor Tae-Woo Lee Develops Long-Lived LED, an Innovative Next-Generation Display Material
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Sep 07, 2020
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A team led by SNU Professor Tae-Woo Lee Develops Long-Lived LED, an Innovative Next-Generation Display Material
- Identification of the cause the existing Perovskite LED short lifespan
- Introduction of 3D-2D hybrid luminescence, reporting an epochal extension of Perovskite LED life
- Introduction of 3D-2D hybrid luminescence, reporting an epochal extension of Perovskite LED life
▲ SNU Professor Tae-Woo Lee
A research team led by Professor Tae-Woo Lee (Dr. Ho-Beom Kim, Researchers Joo Sung Kim and Jung-Min Heo) of the SNU Department of Materials Science and Engineering, Hybrid Materials has developed an LED that will be spotlighted as the next-generation display material. Applying 3D-2D hybrid perovskite material as a luminescent material, this LED dramatically extends the life span that had previously been of only 30 minutes by more than 13 hours, and can produce images of natural colors that are most similar to real objects.
Research and development of next-generation LED that is soon to overtake the organic light emitting diode (OLED), which is currently commercialized, is actively underway. Perovskite is considered one of the most promising luminous materials. Based on the advantages that production is possible at a lower price than existing luminous materials and its high color purity that allows the representation of images that are highly similar to real life objects, it is being spotlighted by the industry as a next-generation display material.
Perovskite LEDs have reported the efficiency of phosphor OLED and quantum dot LED (QDLED) levels in a short period of five years since the first release of the related research. However, the short life span of three-dimensional perovskite LEDs has been pointed out as a problem that must be overcome for commercialization in the future, but until recently, no clear cause or solution has been suggested.
Perovskite is fundamentally a semiconductor material consisting of organic molecules, metals and halogen elements (respectively shown as A, M, and X in Figure a) and usually has a lattice arrangement of three dimensional structures. This material can be applied as a luminous element of LED because of its properties that can convert electrical energy into light energy.
▲ (a) Lattice structure of the 3D perovskite and 3D-2D hybrid perovskite (b) Ion migration suppression mechanism (c) Elemental structure of the developed perovskite LED (d) 3D-3D hybrid perovskite LED’s highly enhanced efficiency in comparison to 3D perovskite LED (e) lifespan and largely reduced luminous overshooting during operation
Professor Lee's team pointed out the high degree rotational freedom of organic molecules (methyl ammonium) located in A position within the perovskite lattice as the cause of the short life of the 3D perovskite LED. In addition, it is claimed that this is a factor that shortens the lifespan of perovskite LEDs because it accelerates fault formation and ionic defect movement (ion migration) within luminescent bodies.
To overcome this problem, Professor Lee's team has developed 3D-2D hybrid perovskite luminescence that has three- and two-dimensional pervoskite co-existing by inducing the exchange of hydrogen ions (H+) between organic molecules by adding neutral molecules (benzylamine) to the three-dimensional perovskite precursor.
Theorganic molecule (benzyl ammonium) that was newly introduced in position A in the 3D-2D hybrid perovskite lattice has a much lower degree of rotational freedom than the existing organic molecule (methyl ammonium), allowing for it to only suppress fault formation, but also reduce fault density, effectively inhibiting phenomena of ion migration.
In addition, Professor Lee's team presented a new measure to assess the lifespan of perovskite LEDs by correlating 'luminescent overshooting during operation' phenomena with ion migration and quantifying them.
Based on these effects, the result of LED devices that can be operated for more than 13 hours were reported, which is a dramatic improvement over 3D Perovskite LEDs that maintain a life span of about 30 minutes.
"We have proposed a way to dramatically extend the life span of perovskite LEDs by adjusting the dimensions of perovskiteluminescence," said Professor Tae-Woo Lee. "This research is expected to not only serve as a guideline for improving the lifespan of perovskite photomultiplier devices, but also contribute to the commercialization of perovskite LEDs as next-generation displays," he aded.
In recognition of its importance, the study was published online on July 6 in Nature Communications, a world-renowned international journal.