A Golden Sandwich


Gold is an extraordinary element. Its illuminating luster has, throughout history, been associated with prestige and opulence. Homer, in The Illiad and The Odyssey, referred to gold as the “glory of immortals and a sign of wealth among ordinary people.”

Chemically, gold is a transition metal known for its malleability and low reactivity. Recently, scientists have discovered that its nanoparticles are incredibly useful in improving the efficiency of solar cells.

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Gold nanoparticles produce a phenomenon called localized plasmon resonance (LSPR) which allows them to absorb certain wavelengths of light. When gold nanoparticles absorb light, the energy excites electrons, freeing them for transfer to a semiconductor.

By embedding gold particles in the polymer layer of solar cells, scientists have discovered a way to take advantage of localized surface plasmon resonance. And when strategically positioned, gold nanoparticles allow a greater percentage to be converted into electrical energy.

A team of scientists at Hokkaido University, led by Professor Hiraoki Misawa of the Research Institute for Electronic Science, has worked to develop a photoelectrode that can efficiently harvest visible light. Initially, the team applied one layer of gold nanoparticles on a semiconductor. That layer took in light within a narrow spectral range. However, it did not provide optimal light absorption.

Therefore, the team began layering the gold nanoparticles around the semiconductor in a sandwich formation to create a mirror effect, trapping light between gold layers. This positioning allowed the nanoparticles to absorb more light, enhancing conversion efficiency. The results of their study were published in Nature Nanotechnology.

“Our photoelectrode successfully created a new condition in which plasmon and visible light trapped in the titanium oxide layer strongly interact, allowing light with a broad range of wavelengths to be absorbed by gold nanoparticles,” says Hiroaki Misawa.

More than 85% of all visible light was harvested by the photoelectrode, which was far more efficient than previous methods. “The light energy conversion efficiency is 11 times higher than those without light-trapping functions,” explains Misawa.

What are your impressions? How might this increased efficiency influence solar adoption? How do you predict it may impact solar market expansion? De Bug Web

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