Study of light trapping in atandem plasmonic solar cell

Abstract

Silicon solar cell photovoltaics offer the possibility of harvesting almost limitless electromagnetic energy radiated from the sun. However, wide-spread adoption of these solar cells requires that greater conversion efficiencies can be attained at cheaper costs than that available with current bulk silicon solar cell technologies. Fundamental loss mechanisms such as the transparency of the materials at longer wavelengths and carrier thermalization effects can be greatly reduced by realizing tandem solar cells. On the other hand, a thin film solar cell with proper photon management can absorb adequate light with low material consumption. Subwavelength nanostructures, especially plasmonic nanostructures have emerged as an exciting research area to increase the light trapping in thin film solar cells. In this thesis, we have investigated light management of a-Si/ c-Si tandem thin film solar cells with metallic nanostructures supporting plasmonics usingFDTDnumerical tool. Our study shows that coupling light to the bottom active region ( c-Si) is challenging at shorter visible wavelength regime of solar spectrum in a a-Si/ c-Si tandem structure due to high absorption coefficient in a-Si top active layer and light management structures are required to enhance bottom layer absorption. Monolithically grown tandem solar cells are susceptible to current mismatch in different active region. We have investigated intermediate metal contact layer with light opening for the bottom active layer as an new approach to make tandem structure insensitive to current mismatch. In our study, we found an overall absorption of 61% in 300 nm of active material of silicon.