SNU Professor Gwan-Hyoung Lee's Research Team Develops the World's Highest Efficiency Light Emitting Diode Based on Two-Dimensional Materials

- Applicable to next-generation optoelectronic circuits
- Light emitting field effect transistor capable of multi-operation mode


▲ Professor Gwan-Hyoung Lee, Doctor and the Research Paper Cover Image

 
A team led by Professor Gwan-Hyoung Lee of the SNU Department of Materials Science and Engineering,Hybrid Materials has developed a light-emitting field effect transistor with a two-dimensional material heterogeneous structure that enables gate voltage regulation and multiple operating modes. Not only can it be used as a triad device due to its multi-function mode, it is also the world's most efficient luminous element that can be used in various fields such as next-generation photomultiplier circuits.
 
This element has recorded the highest luminous efficiency among the two-dimensional material-based luminescence elements present so far and proved that multi-mode operation is possible by gating (voltage transmission within the channel through a gate), and was published online in Advanced Materials, a world-renowned scientific journal in September 2020 and was selected to be the cover image of the journal.
 
Transitional metal dichalcogenides (TMD), a two-dimensional semiconductor material, is thin in its width with the high binding energy of exciton (particles with electrons and holes combined), enabling high-efficiency light emission. The electrical properties of these materials are also very advanced, making them a promising material for next-generation photomultiplier devices. However, until now, it has been difficult to efficiently inject electrons and holes into TMD at the same time, so light emitting elements based on this have shown low light efficiency.
                                       
To overcome these problems, Professor Gwan-Hyoung Lee and Professor Chul-Ho Lee of KU-KIST Graduate School of Converging Science & Technology developed high-efficiency luminous field-effect transistors in two-dimensional heterogeneous structure-based multi-functional mode using field-controlled doping as electrodes and single layer WSe2, a type of bipolar TMD that can transport both electrons and holes.
 
The bonding of metals and semiconductors creates a large energy barrier between the two, which is no exception between the metallic graphene and the semiconductor WSe­2. Professor Lee's team used this barrier as a key to selectively inject electrons and holes. Since it is possible for graphene doping by an external field, this barrier is also adjustable, sometimes by raising barriers to electrons or by raising barriers to holes to prevent the injection of opposing charges.
                                                                     
Thus, the density of electrons and holes entering WSe2 was equal in each of the two graphene electrodes to create the optimal luminous environment, and the number of electrons and holes injected into the WSe2 luminescent layer was optimized to achieve high luminous efficiency at room temperature. In addition, the transistor can be applied to next-generation photomultiplier circuits as it can independently control the luminescence and current flow of light through gate control.
 
Professor Gwan-Hyoung Lee expressed his feelings by saying that, "After five long years of research, we have been able to implement photomultiplier devices through two-dimensional materials such as graphene and dramatically improve its performance. It is expected that photomultiplier devices, which consist of only two-dimensional materials through the control of the work function of graphene, will be used in next-generation photomultiplier circuits and are expected to be used in the future."He expressed his feelings.
 
Published Research Paper
<Multi-operation mode light-emitting field-effect transistors based on van der Waals heterostructure.>


Participating Researchers
Jun-young Kwon (Yonsei Univerisity, Samsung Advanced Institute of Technology), Joon-cheol Shin.Heejae Ryu (SNU), Jae-yoong Lee (Korea University, Dong-jae Seo (University of Minnesota), Kenji Watanabe∙Takashi Taniguchi (National Institute for Materials Science, Japan), Young-deok Kim (Kyung Hee University), James Hone (Columbia University), Chul-Ho Lee (Korea University, Corresponding Author), Kwan-Hyoung Lee (SNU, Corresponding Author)