Design of nanophotonic structures for spectral splitting

In this thesis, a structure is designed to make spectral splitting for parallel junction solar cells. Parallel junction InGaP/GaAs solar cell design was also proposed in order to evaluate the performance of the spectral splitting device. In this context, spectral splitting methods and the studies in the literature are explained in detail. In addition, solar cells and semiconductors have been emphasized in order to provide the necessary knowledge for designing solar cells. Since the designed spectral splitting structure was formed using diffraction gratings, the diffraction gratings were also analyzed in detail. In this context, the design of an optical element with diffraction property, which divides the solar spectrum into two separate parts for a laterally aligned InGaP/GaAs solar cell is presented. Optical simulations were performed using the three-dimensional finite difference time domain method and the results were shown in detail to evaluate the optical performance of the designed structure. An anti-reflection coating design was also proposed for the designed splitter and its effects were demonstrated. In addition to optical analysis, electrical simulations were performed to demonstrate the electrical performance by integrating the designed spectrum splitter onto the InGaP/GaAs solar cell and the curves of current density and power density versus voltage are presented separately. The results of electrical simulations show that the designed parallel junction InGaP/GaAs solar cell has the best efficiency of 16.8% under unconcentrated sunlight. Further improvements can be achieved if the parameters of the spectral splitting device are optimized by the inclusion of non-heuristic optimization algorithms. In addition, light trapping methods may be considered to increase the efficiency of the designed solar cell. In addition to the spectral splitting design, a nano grating design for light trapping for Si solar cells was realized. Therefore, light trapping methods are also described in detail. In this study, a new anti-reflection coating design with reduced reflection losses and focusing is proposed to increase the light capture and absorption efficiency in photovoltaic applications. The design offers an effective combination of anti-reflection coating and grating lens in a single structure. The proposed structure can be a good candidate to increase the efficiency of solar cells.