Electromagnetic Radiation

• Solar cells convert the energy in visible light into electricity. Light, also known as electromagnetic radiation, does not normally damage the materials that make up solar cells. Since ultraviolet light (UV) has more energy than visible light, it can degrade solar cells over time, depending on the type and strength of the UV. Solar cells have a coating of glass or other UV-absorbing materials, effectively preventing this kind of damage.
  
  

Radiation Belts

• The Earth's magnetic field protects us from radiation coming from the sun and space. This radiation, in the form of protons and other charged subatomic particles, becomes trapped in the magnetic field, forming the Van Allen radiation belts. Anything moving through these areas, including satellites, encounters this radiation. The satellites' solar cells must handle years of radiation exposure.
  
  

Silicon

• A cornerstone of modern electronics, silicon found early use in making solar cells. However, when the first communications satellites were launched in the 1950s, scientists noticed that they failed prematurely. Their solar cells were being degraded by Van Allen belt radiation. While manufacturers still use silicon for solar cells today, these cells are used for earthbound applications like rooftop solar panels.
  
  

Gallium Arsenide

• Another semiconductor, gallium arsenide, can produce electricity from light as silicon does. This more expensive material resists the radiation in earth orbit better than silicon, and solar cells made of it last longer in space. Satellites are costly and maintenance on them is difficult, so satellite companies can easily justify the greater expense of gallium arsenide solar cells.
  
  

Indium Gallium Nitride

• As of 2010, scientists are still studying indium gallium nitride for use in solar cells. This semiconductor has been used to make light-emitting diodes (LEDs) that glow in ultraviolet, blue and other colors. It has the potential for replacing gallium arsenide for solar cells as it is less expensive and turns light into electricity more efficiently. Like gallium arsenide, it has high resistance to radiation damage.