RESEARCH I REVIEW


To test their idea, the researchers compared two different silica covering designs: one a fl at surface approximately 5 millimetres thick and the other a thinner layer covered with pyramids and micro-cones just a few microns (one-thousandth of a millimetre) thick in any dimension. The size of these features was essential. By precisely controlling the width and height of the pyramids and micro-cones, they could be tuned to refract and redirect only the unwanted infra-red wavelengths away from the solar cell and back out into space.


“The goal was to lower the operating temperature of the solar cell while maintaining its solar absorption,” said Fan. “We were quite pleased to see that while the fl at layer of silica provided some passive cooling, the patterned layer of silica considerably outperforms the 5 mm-thick uniform silica design, and has nearly identical performance as the ideal scheme.”


Zhu and his colleagues are currently fabricating these devices and performing experimental tests on their design. Their next step is to demonstrate radiative cooling of solar cells in an outdoor environment. “We think that this work addresses an important technological problem in the operation and optimization of solar cells,” he concluded, “and thus has substantial commercialization potential.”


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Journal Reference: L. Zhu, A. Raman., K. Wang, M. Anoma, S. Fan, “Radiative Cooling of Solar Cells,” Optica 1, 32-38 (2014).


Issue IV 2014 I www.solar-international.net 75


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