A study of the suitability of amorphous, hydrogenated carbon (a-C:H) for photovoltaic devices
Amorphous, hydrogenated carbon (a-C:H) is a prospective material for photovoltaic energy conversion because its electronic bandgap can be varied over an unusually wide range (0.4-4.1 eV). Therefore, the suitability of a-C:H for photovoltaic devices has been investigated. Two vacuum deposition techniques, electric arc evaporation and DC magnetron sputtering, were used to deposit a-C:H films. These films were analyzed with respect to their elemental composition by Rutherford backscattering and elastic recoil spectroscopy. The absorption coefficients and the optical bandgap energy were determined using UV/VIS spectroscopy. The electrical resistivity of a-C:H films as well as the activation energy of the conduction process were studied. Subsequently, ohmic contacts to a-C:H were identified and Schottky contacts and heterostructures were fabricated. These devices were characterized by their current-voltage characteristics and quantum efficiency curves. It is found that a-C:H does contribute to the photogenerated current, however, the conversion of photon energy into electric current is not performed efficiently. Partially this is due to a mobility bandgap energy in a-C:H that is much larger than the optical bandgap energy. The localization of electron energy states in the bandtails with the associated retardation of transport properties appears to be responsible for the location of the maximum quantum efficiencies in the UV region.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:amorphous hydrogenated carbon a c h photovoltaic devices elastic recoil spectroscopy optical bandgap energy
Date of Publication:01/01/1997