1.5. Different generations of solar cells
The solar cell can be categorized into four generations. First generation solar cells are based on p–n junction. They are made of c-Si (Si or Ge doped with phosphorous or boron). They are still dominating the marker share (about 80% of market share) as they are most efficient (about 22–24%). Because of having indirect band gap, its absorption coefficient in visible region is low and therefore a thicker absorber layer is required for achieving higher efficiency. Some light trapping techniques are used for increasing the efficiency. Second generation solar cells are based on thin films. Example includes amorphous Si, polycrystalline Si, CIGS, CdTe, CZTS, etc. Third generation solar cells are quantum dot based solar cells. Examples are multi-junction (other than Si), dye, organic, polymer etc. based solar cells. Fourth generation solar cells are based on hybrid-inorganic crystals within polymer molecules.