On the broadband continuous polarization-independent excitation of surface-plasmon-polariton waves for energy-harvesting applications

In a dye-sensitized solar cell (DSC), the broadband continuous excitation of surface-plasmon-polariton (SPP) waves for both TM- and TE-polarization states was studied theoretically. It was found that a TM-polarized broadband continuous excitation in a DSC can be achieved over a 300 nm wavelength range provided that light is incident through accordingly varying refractive index material atop the DSC while a back-contact metallic grating is incorporated. By neighboring the DSC with another broadband absorbing optoelectronic device, the low energy photons would be guided by the back contact till they reach the neighboring device that can absorb the propagating energy and convert it into electron-hole pairs. Thus, the plasmonic dissipation could be significantly reduced and overall high external quantum efficiency could be attained. Moreover, it is shown that whether the solar cell comprises materials with spectrally decreasing or increasing real relative permittivities [Re(ϵ)], the broadband continuous excitation of SPP waves is possible. For the former case, accordingly varying refractive index material atop the solar cell is used, while for the latter case, light is incident through the ambient air. It is shown that the broadband continuous excitation of TM- and TE-polarized SPP waves is possible, and ways to make it polarization-independent are pointed out. The broadband continuous excitation of SPP waves would be useful for energy harvesting, communications, and bio-sensing applications.