Joseph John Loferski (August 7, 1925 – January 20, 1997) was an American physicist and a professor of engineering at Brown University. The New York Times called him "a pioneer in the development of solar cells". During his long and successful career he focused primarily on photovoltaic cells and their ability to convert the energy in light to electricity. Loferski also wrote and spoke extensively on the physics of semiconductor materials such as silicon, and methods of improving the efficiency of photovoltaic cells. Loferski’s work and that of other early researchers proved that semiconductor devices could produce commercially viable, pollution-free electricity.