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Professor Bright Walker and his research team at the Department of Chemistry developed new polymer-metal ion hybrid electrolyte based on poly(9-vinylcarbazole) and designed new light-emitting transistor through electrochemical doping of the new material

The research team synthesized a new polymer electrolyte doped with metal ions and successfully created an electrochemical light-emitting transistor based on oxide semiconductors to identify its mechanism of light emission. This research was conducted in collaboration with the research teams of Professor Jung Hwa Seo at the Department of Physics, the University of Seoul, and Professor Han-Ki Kim at the Department of Advanced Materials Science and Engineering, Sungkyunkwan University.

This research was featured on the cover of the October 21 issue of Advanced Materials Technologies under the title, “Ambipolar Charge Injection and Bright Light Emission in Hybrid Oxide/Polymer Transistors Doped with Poly(9-Vinylcarbazole) Based Polyelectrolytes.”

Improving the efficiency of light-emitting transistors with polyvinylcarbazole-based polymer-gold ion materials
Light-emitting transistors (LETs) are multifunctional devices that can perform electrical switching and amplification functions of field-effect transistors (FETs) while emitting light in the channel region like light-emitting diodes (LEDs) within the same physical device. They can find a wide range of possible applications in various fields such as display devices, electrically generated lasers, and optical communication devices. But the level of technical maturity has not yet reached the performance envelop required by commercial application, as conventional unipolar light-emitting transistors have low efficiency due to the structural deficiency in electron and hole injection. Namely, building balanced electron-hole injection paths into the light-emitting channel is a critical technical hurdle for the design of high-efficiency LETs.

To address this issue, Professor Walker's research team developed a relatively simple process of adding a very small amount of newly synthesized poly(9-vinylcarbazole) polymer-gold ion material (PVK-Li, PVK-Cu) to the light-emitting layer of the LET, dramatically improving luminescence efficiency. In this process, the team also demonstrated successfully the light-generating mechanism of the LET in which, when an appropriate voltage is applied to the device, the metal ions contained in the electrolyte can move due to the electric field generated inside the light-emitting layer, facilitating electron and hole injection.

Professor Walker pointed out the significance of the research and said, "We expect that the results of this research will enable the efficient and stable operation of light-emitting transistors in the future. It is important basic data for the development of next-generation electronic devices, opening up many practical opportunities in various industrial fields."

This research was supported by the Basic Research Laboratory Support Project, the Mid-career Researcher Support Project, and the Creative and Challenging Research Infrastructure Support Project of the National Research Foundation of Korea.