Manufacturers make solar cells from pure silicon that is treated with phosphorous to produce excess electrons and boron; this generates a deficiency of electrons, creating a semiconductor. The thin silicon disks produced in this process are shiny and require an anti-reflective coating made from titanium dioxide.
Solar modules consist of arrays of solar cells encapsulated with transparent silicon rubber or butyryl plastic. Manufacturers embed individual cells in ethylene vinyl acetate. Assemblers mount the array of cells on a polyester film backing, such as mylar or tedlar, and protect it with a glass or lightweight plastic cover. A steel frame bonded to the assembly with silicon cement surrounds the array. Additional electronic parts and wiring consist mostly of copper.
Charles Fritts used gold-coated selenium to make the first solar cell in the 1880s, which was one percent efficient. Bell scientists Gordon Pearson, Darryl Chapin and Cal Fuller produced the first silicon solar cell in 1954, which was four percent efficient. By comparison, today's silicon solar cells are approximately 15 percent efficient.
Researchers attempt to reduce the cost of solar cells and increase their efficiency. One alternative is using tiny, amorphous silicon and polycrystalline silicon rather than single crystal silicon. Other innovations include minimizing shade and focusing sunlight by using layers of different materials, such as gallium arsenide and silicon, that absorb light at different frequencies, increasing the efficiency of sunlight transmission to the cells.