احمد محمدی اسلامی

In this thesis, we study on optical modes in thin film solar cells in order to increase solar cell yield by using finite element method. We provide structures which can excite a significant number of photonic and plasmonic modes. For this purpose, we put an array plasmonic nanograting under surface of the cell absorbent material that is crystalline silicon, irregularly. It excite plasmonic modes as well as excitation of waveguide modes with diffracting light at angles greater than angle of limit by nanograting. These modes also excite in the area which crystalline absorption is too week. It is shown that the use of anti-reflective coating, consisting of an array of silicon nanograting with different thicknesses and on a regular basis, on the surface of the cell, by increasing the length of the active substance and excitation of new Fabry-Perot modes, in addition to reducing the reflection, the optical absorption increases significantly toward using a structure without anti-reflective coating. Finally, we suggest a structure that its optical absorption is significantly greater than previous structures. In this structure we place silver nanorods into absorbent material on a regular basis and once again irregularly, this makes that more plasmonic and photonic modes excite toward previous structures. We can increase optical absorption with anti-reflective coating at this structure.