Multiple excitations of surface-plasmon-polariton waves in an amorphous silicon p-i-n solar cell using Fourier harmonics and compound gratings

In an amorphous silicon p-i-n solar cell, back contact Fourier harmonics (FH) and compound gratings were studied theoretically, using the rigorous coupled-wave analysis. The FH grating was found to enable more efficient multiple surface-plasmon-polariton (SPP) wave excitations compared with a compound grating, while both of them are made of the same constituting simple gratings. The incident plane wave was considered to be TMpolarized. The FH and compound gratings were designed to excite multiple SPP waves at desirable wavelengths by solving a canonical boundary-value problem. The excitation of SPP waves is indicated by the presence of peaks in the absorptance plots. The multiple SPP waves excited by the FH grating were found to increase the external quantum efficiency.