For materials in solar cells, cell phones, and other devices, the material should not change in undesirable ways when exposed to sunlight. Scientists determined how two glasses with the same composition but different fabrication processes behaved when exposed to light. Each glass had a carbon-based chemical composition. Vapor-deposited organic glass, where constituents were vaporized and combined as they were deposited on a surface to form a glass, was substantially more stable than ordinary organic glass. In ordinary glass, the chemicals were melted together and cooled. The molecules in the vapor-deposited glass were more densely packed than the liquid-cooled glass.