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Nanotech Solar Sandwich Can Boost Cell Efficiency

Princeton University scientist have found a simple and cost-effective method to nearly triple the efficiency of solar cells, using cheap and flexible plastic materials that could possibly be the future of solar power.

The team, led by electrical engineer Stephen Chou, used nanotechnology to create a “sandwich” structure of metal and plastic to collect and trap light, increasing cell efficiency to 175 percent.

The nanotech solar sandwich aims to address the main reasons why standard solar cells do not absorb all available sunlight: much of the sunlight is reflected off the cell, which means not all available sunlight is converted to electricity.

Photo Credit: Princeton University

This solar cell sandwich is called a “plasmonic cavity with subwavelength array” or PlaCSH. It can dampen reflection and trap sunlight, reflecting only four percent and absorbing as much as 96 percent of it. This makes the PlaCSH solar cell 52 percent higher in efficiency than a standard solar cell when it comes to converting solar energy to electricity.

The PlaCSH solar cell sandwich consists of five very thin layers. The top layer is the “window layer,” which sunlight hits first, and uses an fine metal mesh that is only 30 nanometers thick. It has holes 175 nanometers in diameter and 25 nanometers apart.

Next is a layer of transparent plastic, followed by a layer of semiconductive material, another layer of titanium oxide and an aluminum layer at the bottom. The combined thickness of all five layers is just 230 nanometers.

“It’s like a black hole for light. It traps it,” said Chou.

The scientists said these PlaCHS solar cells can be manufactured using a cost-effective method in wallpaper-size sheets. The Princeton lab uses a “nanoimprint” technique that Chou invented 16 years ago, which embosses these nanostructures over a large area, similar to printing newspaper.

Besides providing greater efficiency, the materials used could replace the expensive indium-tin-oxide (ITO) electrodes found in standard solar cells, further helping to bring down the costs of solar PV. And with PlaCHS being more flexible than ITO, it could make the solar cells even less fragile.


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