GC: n
CT: The thermal excitation of a carrier from the valence band to the conduction band creates free carriers in both bands. The concentration of these carriers is called the intrinsic carrier concentration, denoted by ni. Semiconductor material which has not had impurities added to it in order to change the carrier concentrations is called intrinsic material. The intrinsic carrier concentration is the number of electrons in the conduction band or the number of holes in the valence band in intrinsic material. This number of carriers depends on the band gap of the material and on the temperature of the material. A large band gap will make it more difficult for a carrier to be thermally excited across the band gap, and therefore the intrinsic carrier concentration is lower in higher band gap materials. Alternatively, increasing the temperature makes it more likely that an electron will be excited into the conduction band, which will increase the intrinsic carrier concentration. This translates directly to solar cell efficiency.
S: http://pveducation.org/pvcdrom/pn-junction/intrinsic-carrier-concentration (last access: 22 February 2015)
N: The minority-carrier concentration, the intrinsic-carrier concentration and the built-in electric field are analysed for a heavily boron-doped silicon with nonparabolic energy bands. In comparison with the intrinsice carrier concentration and the built-in electric field with a degenerate approximation, it is clear that it is necessary to adopt non-parabolic energy bands at high doping concentrations.
S: http://www.tandfonline.com/doi/abs/10.1080/002072196136337?journalCode=tetn20#.VHSmP9KG-So (last access: 22 February 2015)
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