Solar-powered calculators are hand-held electronic calculators powered by solar cells mounted on the device. They were introduced at the end of the 1970s. Amorphous silicon has been used as a photovoltaic solar cell material for devices which require very little power, such as pocket calculators, because their lower performance compared to conventional crystalline silicon solar cells is more than offset by their lower cost and simplified deposition onto a substrate. The first solar-powered (non-scientific) calculators available in the late 1970s included the Royal Solar 1, the Sharp EL-8026, and the Teal Photon. Scientific solar-powered calculators appeared in 1982.