Eccentric nanoshell integration for enhanced light absorption in thin-film solar cells

This work investigates the integration of eccentric nanoshells into thin-film silicon (Si) solar cells to enhance optical absorption. The nanoshells function as efficient light-trapping elements that enhance forward scattering and electromagnetic field coupling into the underlying Si layer. An analytical scattering model, based on a progressive matrix formulation combined with multipole expansion, is used to obtain rigorous electromagnetic solutions, while finite-difference time-domain (FDTD) simulations provide full-wave evaluation of the device response. The results show that the inner-cavity radius and the eccentric displacement strongly influence the scattering strength and the spectral locations of the dominant resonant modes. The optimized design, featuring an outer shell radius of 350 nm and a cavity displaced opposite to the incident direction, achieves an integrated absorption of 77.93%, which is more than three times higher than the planar reference cell (23.62%) over the 300–1100 nm range. The corresponding optically estimated upper-limit short-circuit current density reaches 28.88 mA/cm 2 under the AM1.5 solar spectrum, assuming unity internal quantum efficiency and ideal carrier collection. The corresponding electric-field profiles confirm that the eccentric geometry enhances field confinement within the nanoshell and efficiently channels optical energy into the underlying Si substrate, thereby improving carrier-generation potential. These findings highlight eccentric nanoshells as a promising structural platform for high-performance and cost-effective ultrathin Si solar cells.