11 December 2019
Your office windows could soon be replaced with solar panels, as scientists have found an easy way to turn the green technology transparent. The trick is to punch tiny holes in them that are so close together that we see them as clear.
See-through solar panels will be crucial to increasing the uptake of solar power in cities, says Kwanyong Seo at the Ulsan National Institute of Science and Technology, South Korea.
This is because roof space remains relatively fixed, whereas window space is growing as buildings get taller. “If we apply transparent solar cells on windows of buildings, they can generate huge amounts of electric power every day,” says Seo.
The problem with recently developed transparent cells is that they are often less efficient. They also tend to give the light that passes through them a red or blue hue.
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To overcome this, many scientists are searching for new materials to build transparent cells with. However, Seo and his colleagues wanted to develop transparent solar cells from the most commonly used material, crystalline silicon wafers, which are found in about 90 per cent of solar cells worldwide.
They took 1-centimetre square cells made from crystalline silicon, which is entirely opaque, then punched tiny holes into them to let the light through.
The holes are 100 micrometres in diameter, around the size of a human hair, and they let 100 per cent of the light through without changing its colour.
The solid part of the cell still absorbs all of the light that hits it, which results in a high power-conversion efficiency of 12 per cent. This is substantially better than the 3 to 4 per cent that other transparent cells have achieved, but remains lower than the 20 per cent efficiency that the best entirely opaque cells currently on the market have.
In the coming years, Seo and his colleagues hope to develop a cell that has an efficiency of at least 15 per cent. To make the product marketable, they will also need to develop an electrode that is transparent.
Journal reference: Joule, DOI: 10.1016/j.joule.2019.11.008
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