Currently, the surface-plasmon-polariton (SPP) waves can be excited only at certain wavelength and certain incidence angle. It is remarkably noticed that the wavenumber of the SPP waves decreases as the incident wavelength increases. This stands against the continuous excitation of SPP waves at certain incidence angle using a practical grating configuration. We hypothesized that the theoretical modeling of SPP waves guided by the interface of a dielectric grating and a metal will help to solve that problem. The aim of the study is to prove that the proposed grating/metal configuration has propensity of guiding SPP waves of relative wavenumber that increases as the incident electromagnetic wavelength increases. This may enable the continuous excitation of SPP waves. The successful attempt of proving the aim of this study will validate the excitation of SPP waves at certain incidence angle but at wider range of incident wavelength. This result will have a great impact on the communication and energy harvesting applications.
The rigorous coupled wave analysis (RCWA) is used to solve the Maxwell equations in its differential form. The Newton-Raphson method is used to solve the dispersion equation at the grating/metal interface for the SPP wavenumber. This provides the wavenumber of the SPP waves that can propagate at the grating metal interface. A study for the SPP wave energy decay will also be made through the calculation of the Poynting vector, and show that the propagating SPP waves decay away from the grating/metal interface, which infers the surfacing property of the propagating waves.
A p-i-n solar cell is best suited for strong absorbers with poor collection capabilities. However, the absorption naturally decreases at photon energies close to the electronic bandgap of the semiconductor. We hypothesized that a quasi-periodic surface textures in the role of diffraction gratings at the back contact can efficiently scatter light increasing the optical path length inside the absorber layer. The effect of quasi-periodic corrugated backing metallic contact of various types was studied theoretically. To help optimizing the design of the quasi periodic grating the corresponding canonical problem was considered. The absorption of light was calculated using the rigorous coupled-wave approach. The n- and i-layers consist of isotropic nonhomogeneous multilayered semiconductor.
The intrinsic layer in an amorphous-silicon solar cell is usually several orders of magnitude thicker than the p- and n-layers to increase the electron-hole pair generation in the intrinsic layer and to decrease the recombination losses in the p- and n-layers. We hypothesized that a nohomogeneous intrinsic layer may trap the incident light better and increase the generation rate of charge carriers. The nonhomogeneity can be introduced by varying the composition of amorphous silicon alloys during chemical vapor deposition. The effect of intrinsic layer nonhomogeneity of various schemes was studied theoretically on the short-circuit current of a single-junction thin-film amorphous-silicon solar cell. The absorption of light was calculated using the rigorous coupled-wave approach for an AM1.5 solar irradiance spectrum for a wavelength range of 400-1100 nm. An antireection coating consisting of two layers of homogeneous dielectric materials was also used. The backing metallic layer of the solar cell was taken to be periodically corrugated. The short-circuit current of the solar cell with nonhomogeneous intrinsic layer was found to be higher than the solar cell with a homogeneous intrinsic layer.