Amorphous Silicon-Carbon Nanostructure Photovoltaic Devices

A novel solar cell architecture made completely from the earth abundant elements silicon and carbon has been developed. Hydrogenated amorphous silicon (aSi:H), rather than crystalline silicon, is used as the active material due to its high absorption through a direct band gap of 1.7eV, well matched to the solar spectrum to ensure the possibility of improved cells in this architecture with higher efficiencies. The cells employ a Schottky barrier design wherein the amorphous silicon absorber layer generates electron-hole pairs from incoming photons and holes are preferentially extracted through a metallic material consisting of a carbon nanostructure. Both graphene and buckypaper were used as the metallic component of the Schottky junction to effectively convert incoming light to electricity. Subsequent work focused on graphene-based cells because graphene offers better transparency and conductance compared to buckypaper, making it promising as a top conductor in a solar cell. Reactions of the graphene-aSi:H interface were investigated and strategies developed to minimize reactions that lead to performance degradation. Finally, photon management strategies were executed to significantly enhance the performance of the cells using silver nanoparticles to increase the absorbance of light and extraction of charges in a thin aSi:H film. Solar cells optimized with these improvements show performance enhancements of 1-2 orders of magnitude compared to initially published cells in this architecture.In addition to yielding strategies for improved protection and performance of the solar cells presented in this thesis, investigations presented here into reactions at the graphene-silicon interface should inform further research into applications of graphene