Sungkyunkwan University researchers have developed a volatile surface reconstruction technique using potassium acetate to heal chemical defects in lead-free tin-based perovskite semiconductors, achieving world-class p-type transistor performance with hole mobility exceeding 50 cm²/V·s and stable operation exceeding four hours in air.
Transistors control electrical signals across countless modern electronic devices, ranging from everyday consumer smartphones to complex computing infrastructure. They rely on an essential balance between n-type transistors, which use electrons as charge carriers, and p-type transistors, which operate using the vacant spaces left behind by electrons. Achieving parity between these two carrier types remains vital for developing low-power, high-performance semiconductor technology. Yet, improving p-type transistor capability has long presented a formidable technical hurdle, earning formal recognition from the Ministry of Science and ICT as one of the 10 Future Challenges in the Semiconductor Field
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Overcoming Surface Oxidation in Eco-Friendly Tin-Based Perovskite Semiconductors
Tin-based perovskite semiconductors have emerged as a leading eco-friendly alternative to toxic lead-based materials, offering exceptional hole transport properties suited for advanced p-type transistors. However, exposing these materials to atmospheric oxygen triggers rapid degradation. Unreacted and undercoordinated tin ions sitting on the semiconductor surface oxidize easily, creating structural defects that disrupt efficient charge transport and cause performance and lifespan to deteriorate swiftly.
To solve this instability, a joint research team led by Professor Ji-Sang Park at the Sungkyunkwan University (SKKU) Advanced Institute of Nanotechnology (SAINT), alongside Professor Yong-Young Noh’s team at the Pohang University of Science and Technology (POSTECH) and teams led by Professors Ao Liu and Huihui Zhu at the University of Electronic Science and Technology of China (UESTC), engineered a targeted chemical treatment. The researchers treated the surface of a cesium–tin–iodide semiconductor with potassium acetate.
During this volatile surface reconstruction process, unstable tin species on the exterior—the primary catalysts for material degradation—convert into volatile compounds and disperse away from the surface. Simultaneously, potassium iodide naturally forms directly within the spaces left behind by the departed tin ions. This sequence builds a self-passivating protective barrier that effectively blocks future exposure to moisture and ambient air.
World-Class Performance and Stability Metrics in Published Research
The breakthrough findings were detailed in Nature, one of the world’s most prestigious scientific journals, following publication on July 1. By removing defect sources and simultaneously sealing the surface with an iodide layer, the international team achieved world-class operating metrics for p-type perovskite transistors.
| Performance Metric | Conventional Perovskite Devices | Newly Developed Potassium Acetate-Treated Devices |
|---|---|---|
| Hole Mobility | Unstable / Degraded | Exceeding 50 cm²/V·s |
| On/Off Current Ratio | Unstable / Degraded | More than 10⁸ |
| Ambient Air Lifetime | Degrades within minutes | Exceeding four hours of stable operation |
| Thermal Stability at 100°C | Rapid failure | Retained initial performance for over one month |
Professor Ji-Sang Park emphasized the broader scientific implications of discovering these specific chemical pathways.
Beyond simply enhancing device performance, this study was especially meaningful because we were able to identify the specific chemical reaction pathways and defect-healing principles of volatile surface reconstruction. Elucidating this mechanism in close collaboration with our domestic and international partners was deeply rewarding, especially as we expect this approach to be broadly applicable to other next-generation semiconductor materials.
Professor Ji-Sang Park, Sungkyunkwan University Advanced Institute of Nanotechnology
Funding Support and Future Applications Across Electronic Systems
The collaborative project received financial backing from the Leader Research Program and the Mid-Career Researcher Program managed by the National Research Foundation of Korea, along with corporate support from Samsung Display. By verifying that volatile surface reconstruction can successfully eliminate oxidation risks without sacrificing electrical behavior, the research paves the way for commercial, eco-friendly semiconductor applications that bypass traditional toxic heavy metals.
