Rahul Dewan

• For silicon based thin-film solar cells, photon management strategies such as efficient light incoupling and light trapping within the absorbing material are imperative for realizing efficient solar cells. In this thesis, the optical enhancements in microcrystalline thin-film silicon solar cells with periodic surface texture were investigated. Using Finite Difference Time Domain (FDTD) and Rigorous-Coupled Wave Analysis (RCWA) algorithms, the optical wave propagation in the solar cell structure was calculated by rigorously solving the Maxwells equations in two- and three-dimensions. By studying the influence of the period and height of the surface texture, the design of the structures were optimized to achieve higher short circuit currents and quantum efficiencies. Enhancement of the short circuit current in the blue part of the spectrum (wavelengths 300-500 nm) is achieved for smaller periods of the texture (P<200 nm), whereas the short circuit current in the red and infrared part of the spectrum (wavelengths 700-1100 nm) is increased for periods of the texture (P=900nm) comparable to the optical wavelength. Furthermore, the influence of the solar cell thickness on the upper limit of the short circuit current was investigated. The numerically simulated short circuit currents were compared to fundamental light trapping limits based on geometric optics. Additionally, the parasitic absorption losses in the solar cell were analyzed. By identifying these key losses, strategies to minimize the losses were also discussed. The results from this thesis show that efficient light trapping techniques, which can guide the propagating light within the absorber layer, becomes more crucial as the solar cells get thinner.