Reviewed by Lexie CornerMar 19 2025
A Korean research team has discovered a method to extend the lifespan of hot holes and increase their flow. This breakthrough accelerates the commercialization of next-generation, high-efficiency light-to-energy conversion technology.
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When light interacts with metallic nanostructures, plasmonic hot carriers are generated. These carriers play a crucial role in converting optical energy into valuable forms of energy, such as electricity and chemical energy. Hot holes are particularly important for enhancing photoelectrochemical reactions, but they tend to evaporate thermally within picoseconds. This rapid evaporation has made their practical use challenging.
On March 12, 2025, KAIST announced that a research team, led by Distinguished Professor Jeong Young Park of the Department of Chemistry, along with Professor Moonsang Lee of the Department of Materials Science and Engineering at Inha University, had successfully amplified the flow of hot holes. They also mapped the local current distribution in real time. This breakthrough clarified the mechanism behind the enhancement of photocurrents.
The team created a nanodiode structure by positioning a metallic nanomesh on a specific semiconductor substrate (p-type gallium nitride) to enable the extraction of hot holes at the surface. As a result, the hot hole flow was approximately twice as large in gallium nitride substrates aligned with the hot hole extraction direction. In comparison, the flow was lower in substrates aligned in other directions.
The process involved initially assembling a polystyrene nano-bead monolayer on a gallium nitride substrate. The beads were then etched to create a nanomesh template for the Au nanomesh. The gold nanomesh structure was formed by removing the etched polystyrene beads after applying a 20 nm thick gold film. The plasmonic resonance effect in the Au nanomesh led to significant visible light absorption.
Additionally, the team used photoconductive atomic force microscopy (pc-AFM) to map the flow of hot holes in real time at the nanometer scale. They identified "hot spots," or localized light concentrations on the gold nanomesh, where hot hole activation was most intense. However, they also observed that hot hole activation spread beyond these hot spots, influenced by the gallium nitride substrate’s development direction.
This research has led to a practical method for transforming light into chemical and electrical energy. The findings could significantly impact the development of hydrogen production, photocatalysts, and next-generation solar cells.
For the first time, we have successfully controlled the flow of hot holes using a nanodiode technique. This innovation holds great potential for various optoelectronic devices and photocatalytic applications. For example, it could lead to groundbreaking advancements in solar energy conversion technologies, such as solar cells and hydrogen production. Additionally, the real-time analysis technology we developed can be applied to the development of ultra-miniaturized optoelectronic devices, including optical sensors and nanoscale semiconductor components.
Jeong Young Park, Professor, Korea Advanced Institute of Science & Technology
Hyunhwa Lee (PhD, KAIST Department of Chemistry) and Yujin Park (Postdoc Researcher, University of Texas at Austin Department of Chemical Engineering) co-led the study. Professors Moonsang Lee (Inha University, Department of Materials Science and Engineering) and Jeong Young Park (KAIST, Department of Chemistry) were the corresponding authors.
The study was supported by the National Research Foundation of Korea (NRF).
Journal Reference:
Lee, H. et. al. (2025) Reconfiguring hot-hole flux via polarity modulation of p-GaN in plasmonic Schottky architectures. Science Advances. doi.org/10.1126/sciadv.adu0086