Science News for Students - Spring 2021

The future of crystal-based solar energy just got brighter Tweaks make more efficient solar cells that can be printed or painted onto anything By Kathiann Kowalski T wo recent innovations are boosting prospects for a new type of solar-energy technology. Both rely on a somewhat unusual type of crystal. Panels made from them have been in the works for about 10 years. But those panels had lots of limitations. New tweaks to their design might now lead to better and potentially less costly solar panels.

(NREL) in Golden, Colo., have been leading efforts to develop this solar technology. They unveiled new developments in October 2019 to visiting reporters. A big industry already exists to make solar panels. Today, al- most all are made from thin but rigid wafers of silicon. Silicon, the basis of sand, is cheap. Making wafers from it is not. The wafers must be made in carefully controlled conditions. And the finished product won’t bend. In contrast, the new solar panels are made with manufac- tured crystals called perovskites. These contain some element with properties like bromine or iodine, plus a metal and other ingredients. A liquid mixture of these can be painted or rolled onto any surface. As the liquid quickly dries, crystals form. The crystals line up in a way that makes themwork well as semiconductors —materials that sometimes conduct electricity. Yet they’re much easier and quicker to make than the crystals in panels of silicon-based solar cells. So covering sheets with these crystals might one day be as fast as printing ink onto rolling panels of paper. But instead of

Photovoltaic panels convert sunlight into electricity. One tweak to the materials designed for use in the new type of panel would let them tap more of the energy in sunlight. A second advance makes it easier to stack layers of this mate- rial into a sandwich. Each layer is most sensitive to different wavelengths, or portions of sunlight. Stacking the layers can harvest more incoming light. Researchers at the National Renewable Energy Laboratory

DENNIS SCHROEDER/NREL

14 SCIENCE NEWS FOR STUDENTS | Invention & Innovation