Broadband efficiency enhancement in quantum dot solar cells coupled with multispiked plasmonic nanostars

We report a significant broadband enhancement of the external quantum efficiency of the quantum dot solar cell by coupling with plasmonic nanostars via a simple and scalable boiling deposition technique. The multispiked nanostars provide broadband scattering and absorption cross-sections, which can be engineered to dramatically boost the performance of the solar cells. The localized near field modes of nanostars result in an external quantum efficiency enhancement over 400% for short-wavelength light absorbed in the emitter, while plasmon light scattering causes distinct improvement in quantum efficiency (10-50%) in the long-wavelength region up to 1100 nm. Finite difference time domain method is adopted to explain the origin of the optical absorption enhancement in the quantum dot solar cells. The broadband light concentration by plasmonic nanostars can significantly reduce the amount of quantum dot materials required for a solar cell and provide efficient utilization of the full solar spectrum. (C) 2015 Elsevier Ltd. All rights reserved.