University of Seoul and Dong-A University Develop High-Sensitivity Phototransistor

Detection of Near-Infrared Signals Achieved at Voltages Below 5V

A joint research team from the University of Seoul and Dong-A University has developed an ambipolar organic phototransistor (OPT) that can implement both P-type and N-type operations in a single organic semiconductor material and detect near-infrared (NIR) with high sensitivity even at low voltages below 5V.

The team also succeeded in detecting real-time changes in near-infrared signals, demonstrating its potential for next-generation sensing technologies such as LiDAR, contactless motion sensors, and wearable photodetectors.

Joint research team of University of Seoul and Dong-A University. From left: researcher HeeHwang Noh, research professor Swarup Biswas, Dong-A University professor Hongju Lee, University of Seoul professor Hyuk Kim. University of Seoul

On October 2, the University of Seoul announced that a joint research team, led by Professor Hyuk Kim from the School of Electrical and Computer Engineering at the University of Seoul and Professor Hongjoo Lee from the Department of Semiconductor Engineering at Dong-A University, has developed a high-sensitivity near-infrared ambipolar organic phototransistor that operates stably at low voltages.

The results of this research were published on April 27 in the international journal *Small*, published by Wiley, under the title "Low-Voltage, High-Sensitivity NIR Ambipolar Organic Phototransistor Based on a Non-Fullerene Acceptor."

Researchers Hwahpyoung Noh and Swarup Biswas participated as co-first authors, with Professor Hongjoo Lee as a co-author and Professor Hyuk Kim as the corresponding author who led the research.

For near-infrared-based sensing systems such as LiDAR, it is crucial to detect weak optical signals with high sensitivity while ensuring stable operation at low voltages.

However, conventional organic phototransistors have faced limitations such as high operating voltages, low charge mobility, and insufficient near-infrared absorption characteristics.

To address these challenges, the research team applied the Y6 organic semiconductor, which exhibits excellent near-infrared absorption, and an Al2O3 insulating layer with high dielectric constant.

Additionally, they utilized an ODPA self-assembled monolayer (SAM) to reduce interface defects and enhance the molecular arrangement and crystallinity of Y6.

As a result, they succeeded in implementing a high-sensitivity ambipolar organic phototransistor capable of both P-type and N-type operation within a single organic semiconductor material, stably detecting near-infrared at low voltages of less than ±5V.

Notably, the research team successfully demonstrated real-time detection of changing near-infrared signals using the developed device.

They clearly detected changes in current signals as a near-infrared laser was repeatedly blocked by finger movements, confirming that dynamic near-infrared signals can also be reliably detected.

This achievement demonstrates the potential for wide application in future low-power, high-sensitivity near-infrared sensing systems, such as LiDAR, contactless motion sensors, and wearable photodetectors.

In particular, the technology is also expected to be utilized as a sensor for detecting surrounding environments and movements in physical AI fields such as humanoids and intelligent robots.

Professor Hyuk Kim commented, "This study is significant in that it makes possible both ultra-low-power continuous operation and high-sensitivity near-infrared detection at low operating voltages, thereby increasing the practical feasibility of next-generation photodetectors. We expect that this technology can be applied to a variety of intelligent sensing fields for LiDAR, contactless sensors, and wearable electronic devices for humanoids and other physical AI applications in the future."

This research was conducted with support from the Mid-career Researcher Program and the Global Research Lab Advanced program of the Ministry of Science and ICT and the National Research Foundation of Korea, as well as the Semiconductor Advanced Strategic Industry Super-Gap Technology Development Project of the Ministry of Trade, Industry and Energy and the Korea Evaluation Institute of Industrial Technology (KEIT). The Semiconductor Research Center (UOS Fab) of the University of Seoul also provided research infrastructure.

This content was produced with the assistance of AI translation services.