Abstract:
The objective of this thesis work is to improve the optical absorption of silicon (Si) solar cell by increasing solar absorption. For this purpose, a hybrid design of silicon (Si) solar cell is designed with guided-mode resonance filter (GMRF) to increase absorption efficiency. The GMRF is a resonant waveguide grating (RWG) structure, which increases the resonant field and enhances the propagation path for light within the cell material. Light confinement in silicon (Si) solar cells through GMRF structure is theoretically demonstrated. The GMRFs are designed in Fourier Modal Method (FMM) using regression algorithm. A hybrid design of Si solar cell with GMRF is designed in the Finite-Difference Time-Domain (FDTD) software. The waveguide grating structure is defined by designing a grating structure in fused silica (SiO2) material coated with a high index thin layer of amorphous titanium dioxide (TiO2) material. The designed waveguide grating structure exhibits a 100% resonance reflectance response at a particular resonance wavelength λr.
One of the possible optimized designed parameters for the waveguide grating structure are: grating period d = 316 nm, grating grooved height hg = 120 nm, structural-line width w = 205 nm, fill factor f = 0.65, refractive index of SiO2 ns = 1.45, refractive index of TiO2 nt = 2.385, thickness of TiO2 layer t = 50 nm, angle of incidence θi = 18o, and resonance wavelength λr = 632.8 nm (Helium-neon laser), whereas, the realizable designed parameters for Si solar cell are: refractive index of Si material N = 3.882 + i(0.019) at resonance wavelength λr = 632.8 nm, cell thickness T = 500 nm. Compared to a planar Si solar cell, approximately 38% enhancement in the optical absorption is achieved over the 550-750 nm wavelength range for a GMRF enabled Si solar cell. This improvement in optical absorption of hybrid device structure inspires the application of Guided-Mode Resonance (GMR) effect in solar cells where increased absorption efficiency is a key demand. The GMRF enabled solar cells possesses the capability to indicate a new hybrid-design concept to improve the optical absorption. An appropriate optimization of grating design parameters in simulation guides to effective hybrid device operation. The theoretical explanation demonstrates the prospective of appropriate designed GMRF characteristics in silicon (Si) solar cells.
