U.S. scientists say that emerging photovoltaic technologies will enable the production of solar shingles made from abundantly available elements rather than rare-earth metals, an innovation that would make solar energy cheaper and more sustainable.

Speaking at the annual meeting of the American Chemical Society, a team of researchers described advances in solar cells made with abundant metals, such as copper and zinc. While the market already offers solar shingles that convert the sun’s energy into electricity, producers typically must use elements that are scarce and expensive, such as indium and gallium.

According to Harry A. Atwater, a physicist at the California Institute of Technology, recent tests suggest that materials like zinc phosphide and copper oxide could be capable of producing electricity at prices competitive with coal-fired power plants within two decades. With China accounting for more than 90 percent of the world’s rare-earth supplies — and prices rising sharply — companies and nations are racing to find new sources of rare earth minerals, which are used in everything from solar panels to smart phones.