Investigation of resonance structures in optically thin solar cells

To reduce costs, the solar cell industry aims at producing thinner solar cells. Structuring the surfaces of optically thin devices is important for avoiding transmission-related losses and, hence, increasing their efficiency. Light trapping leads to longer optical pathlengths and increased absorption of energy. In addition, resonances in the nanostructures enhance the absorption in the energy-converting material. Further, resonances in periodic structures may couple with each other and thereby increase the absorption. Here, we establish a model system consisting of a multilayered solar cell to study resonances and coupling of resonances in a one-dimensional system. We show that resonances in energy-converting and nonenergy converting layers exist, evaluate the resonances and the coupling of resonances in different thin-film systems, and show how they affect the total absorption of energy in the energy-converting layer. We optimize the parameters of the multilayered thin-film systems to achieve an increase in the amount of the absorbed energy. We find that resonances in nonabsorbing material at the top may lead to absorption enhancement, while we cannot find any enhancement effect due to the coupling of resonances.