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In order to reduce costs, the solar cell industry is aiming at producing ever thinner solar cells. Structuring the surfaces of optically thin solar cells is important for avoiding excessive transmission-related losses and, hence, to maintain or increase their efficiency. Light trapping leading to longer optical path lengths within the solar cells is a well established field of research. In addition to this, other possible benefits of structured surfaces have been proposed. It has been suggested that nanostructures on the surface of thin solar cells function as resonators, inducing electric-field resonances that enhance absorption in the the energy-converting material. Further, coupling of electric field resonances in periodically structured solar cells may couple with each other thereby increasing the absorption of energy. A deeper understanding of the nature of the energy-conversion enhancement in surface-structured and thin solar cells would allow to design more targeted structures. Generally, efficiency enhancement may be evaluated by investigating the electric field and optimizing the optical generation rate. Here, we establish a model system consisting of multilayered solar cells in order to study resonances and coupling of resonances in a one-dimensional system. We show that resonances in energyconverting and non-energy converting layers exist. The coupling of resonances in the non-energy converting material and the energy-converting material is only possible for certain parameter ranges of thickness of the energy converting material and the imaginary part of the refractive index. We 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 show how resonances in non-absorbing layers can contribute to increasing the resonances in the absorbing layers. We optimize the parameters of the multilayered thin-film systems to achieve an increase in the amount of the absorbed energy. The optimization is also evaluated for an experimentally realizable thin-film solar cell.
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