Plasmonic metallic nanostructures for efficient absorption enhancement in ultrathin CdTe-based photovoltaic cells

The effects of incorporating metal nanodiscs (NDs) and nanospheres on optical absorptions of a CdTe solar cell are theoretically investigated by finite-difference time-domain calculations. Significant broadband absorption enhancements have been demonstrated in CdTe layers with various metals, among which Al-ND arrays result in the best photon absorption performance of up to 50% enhancement with respect to bare CdTe materials. The origins of increased absorptions are believed to be the effects of the enormous electric field enhancement and increased scattering upon the excitation of localized surface plasmon resonance. The geometrical dependences of photon absorption in plasmonic CdTe thin films are also studied, from which the relatively optimal geometrical parameters leading to the ultimate solar cell efficiency of ∼36% are extracted. Besides, this work offers a clue to using low-cost plasmonic metals for potential photovoltaic applications.