Iron salts are mixed with sulfide salts inside the metal autoclave container at left and heated in an oven for four hours.The result: a black suspension of pyrite nanocrystals.Wadia sets a glass chip on the circular pedestal in the center of a spin-coating machine and then drips the pyrite suspension onto it. A minute of spinning coats the chip with a thin film of pyrite.He uses tweezers to set the chip on a hot plate; 10 to 15 minutes of heat will fix the nanocrystals to the surface.Wadia places a glass chip with eight pyrite solar cells on its surface inside a solar simulator. The aluminum lines are the cells’ top electrical contacts; the line across the top of the chip is a strip of conductive indium tin oxide.Inside the solar simulator, the chip is illuminated with light in a mixture of wavelengths simulating the distribution found in sunlight. Electrical connections to the manifold read the current and voltage across each cell, helping Wadia to calculate its efficiency.
