Comparison of silicon oxide and silicon carbide absorber materials in silicon thin-film solar cells

Abstract

Since solar energy conversion by photovoltaics is most efficient for photon energies at the bandgap of the absorbing material the idea of combining absorber layers with different bandgaps in a multijunction cell has become popular. In silicon thin-film photovoltaics a multijunction stack with more than two subcells requires a high bandgap amorphous silicon alloy top cell absorber to achieve an optimal bandgap combination. We address the question whether amorphous silicon carbide (a-SiC:H) or amorphous silicon oxide (a-SiO:H) is more suited for this type of top cell absorber. Our single cell results show a better performance of amorphous silicon carbide with respect to fill factor and especially open circuit voltage at equivalent Tauc bandgaps. The microstructure factor of single layers indicates less void structure in amorphous silicon carbide than in amorphous silicon oxide. Yet photoconductivity of silicon oxide films seems to be higher which could be explained by the material being not truly intrinsic. On the other hand better cell performance of amorphous silicon carbide absorber layers might be connected to better hole transport in the cell.

Shrinking of silicon nanocrystals embedded in an amorphous silicon oxide matrix during rapid thermal annealing in a forming gas atmosphere

“…As described in section 1, this is within the temperature range at which hydrogen effusion occurs. For both annealing atmospheres the material('s) band gap decreases upon annealing, which is attributed to a decrease in hydrogen caused by hydrogen effusion [22]. Also the sub-band gap absorption increases for both annealing atmospheres, indicating an increase in defect density.…”

Electrodeposition and Characterization of SiOxFilms Photoactive in Organic Solution

“…Due to their properties, SiO x containing systems have been recently attracting an increasing interest as candidates for light absorbing or emitting materials, e.g. in form of amorphous silicon oxide, a-SiO:H, [21][22][23] Si nanoparticles embedded in SiO x matrix, 24,25 SiO x /SiN y multilayers 26 or doped SiO x /SiO 2 multilayers. 27 The common methods of the production of SiO x (and crystalline Si which used to produce high quality SiO x ) are high extremely energy consuming and due to the toxic waste produced, also environmentally hazardous processes.…”