Progress of light to electrical energy conversion: a new method extends the lifespan of plasmonic hot holes

When light interacts with metal nanostructures, it instantly generates plasmonic hot carriers that act as key intermediates for converting optical energy into high value energy sources such as electrical and chemical energy. Among these, hot holes play an important role in enhancing photoelectrochemical reactions. However, they will dissipate thermally within picoseconds (one trillion seconds), making practical applications difficult.

Now, a Korean research team has successfully developed a method to maintain hot holes for longer, amplify their flow, and accelerate the commercialization of next-generation, high efficiency, light-to-energy conversion technologies.

A research team led by Professor Jeong Young Park of Kaist’s Chemistry Department, worked with Professor Moonsang Lee of the Faculty of Materials Science and Engineering at INHA University to map local current distributions that map hot hole flows in real time, thereby elucidating the mechanism of optical expansion. This work is featured in Science Advances.

The team designed the nanodiode structure by placing metal nanomesh on a special semiconductor substrate (P-type gallium nitride) to facilitate hot hole extraction on the surface. As a result, in the gallium nitride substrate aligned in the hot hole extraction direction, the hot hole flow was amplified about twice compared to the other aligned substrates.

To fabricate Au nanomesh, a polystyrene nanobead single-layer assembly was first placed on a gallium nitride (P-Gan) substrate, and then polystyrene nanobeads were etched to form a nanomesh template. Next, 20 nm thick gold nanofilms were deposited to remove etched polystyrene nanobeads to achieve the gold nanomesh structure of the GAN substrate. The manufactured au nanomesh exhibited strong light absorption in the visible range due to the plasmonic resonance effect.

Additionally, using a photoconductive atomic force microscope (PC-AFM)-based photocurrent mapping system, researchers analyzed hot hole flows in real time on a nanometer scale (one thousandth of the thickness of human hair). They observed that hot hole activation was the strongest in “hot spots.” There, light was locally concentrated in the gold nanomesh. However, by changing the growth direction of the gallium nitride substrate, hot hole activation was extended beyond the hot spots to other regions.

Through this research, the team discovered an efficient way to convert light into electrical and chemical energy. This breakthrough is expected to significantly advance next-generation solar cells, photocatalysts and hydrogen production technologies.

“For the first time, we have successfully controlled the flow of hot holes using nanogeode technology. This innovation has great potential for a variety of photoelectronic devices and photocatalytic applications. It could lead to groundbreaking advancements in solar energy conversion technologies, such as solar energy conversion technology and hydrogen production,” said Professor Park.

“In addition, the real-time analytical technology we have developed can be applied to the development of super-based, hardened optoelectronic devices, including optical sensors and nanoscale semiconductor components.”