Scientists have developed a light-absorbent material to cool buildings, cars on hot summer days. The material, developed by engineers at the University of California San Diego in the US, is called a near-perfect broadband absorber. It absorbs more than 87 per cent of near-infrared light (1,200 to 2,200 nanometre wavelengths), with 98 per cent absorption at 1,550 nanometres, the wavelength for fiber optic communication. The material is capable of absorbing light from every angle. It also can theoretically be customized to absorb certain wavelengths of light while letting others pass through. Materials that “perfectly” absorb light already exist, but they are bulky and can break when bent. They also cannot be controlled to absorb only a selected range of wavelengths, which is a disadvantage for certain applications. The new material offers broadband, yet selective absorption that could be tuned to distinct parts of the electromagnetic spectrum, researchers say. Engineers designed and built an absorber from materials that could be modified, or doped, to carry a different amount of free electrons: semiconductors. Researchers used a semiconductor called zinc oxide, which has a moderate number of free electrons, and combined it with its metallic version, aluminum-doped zinc oxide, which houses a high number of free electrons. They created a nanotube array using advanced nanofabrication technologies. The resultant material was thin, flexible and transparent in the visible. The technology is still at the developmental stage. The work was published in Proceedings of the National Academy of Sciences.
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