Study Achieves 3x Performance Boost in Organic Photodetector Devices, Published in Nature Sister Journal

Professor Park Songyi of Pukyong National University Identifies Properties of Organic Semiconductors for High-Performance Organic Photodetector Devices

A research result has emerged that draws attention, showing that the performance of organic photodetector devices?rising as next-generation image sensors?can be increased by more than three times compared to existing devices.

Professor Songi Park, Pukyong National University.

Professor Park Songyi (Department of Physics) at Pukyong National University recently published research results in the international journal 'Nature Communications,' identifying the properties of organic semiconductor materials that can enhance the detectivity of organic photodetector devices and simplify the fabrication process.

A photodetector is an electronic device that converts light into electrical signals. It is used not only in camera image sensors but also in health monitoring sensors for wearable electronic devices such as smartwatches. Among them, organic photodetectors, which use organic semiconductors with excellent light absorption, tunable bandgaps, and physical flexibility as the photoactive layer, are attracting attention as next-generation photodetectors and are actively researched worldwide.

In this study, Professor Park Songyi revealed that the high octupole moment of the subphthalocyanine compound (Cl6-SubPc) plays a key role in the generation of free charges under light irradiation.

Typically, organic semiconductors form electron-hole pairs called excitons under light irradiation, but their strong binding energy prevents them from easily separating into free electrons and holes at room temperature. To overcome this strong binding energy, organic photodetectors mainly use bulk-heterojunction (BHJ) photoactive layers, created by randomly mixing two or more materials, or planar-heterojunction (PHJ) photoactive layers, made by stacking two materials.

Image related to research by Professor Park Songi.

According to Professor Park Songyi's research, Cl6-SubPc molecules induce an electrostatic potential difference within the thin film due to their high octupole moment, which leads to intrinsic energy level separation. This energy level difference allows excitons to be easily separated into free electrons and holes.

In this study, she fabricated a PHJ-based organic photodetector device using Cl6-SubPc as the main photoactive layer and MPTA as the auxiliary photoactive and hole transport layers. Analysis of its photoelectric properties showed a detectivity of approximately 10¹³ Jones at a wavelength of 590 nm. This is more than three times higher than the performance of previously reported PHJ-based organic photodetector devices.

Professor Park stated, "By using materials with a high octupole moment like Cl6-SubPc, it is possible to realize high-performance photodetector devices with a single material and a single layer, dramatically simplifying the fabrication process and potentially accelerating the commercialization of organic photodetectors."

Professor Park Songyi, the first author of this study, conducted this international joint research with Imperial College London in the UK and Samsung Advanced Institute of Technology.

The research paper, titled 'Octupole moment driven free charge generation in partially chlorinated subphthalocyanine for planar heterojunction organic photodetectors,' was published in 'Nature Communications' on June 13.

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