In recent times, thin-film solar cells have gained a lot of attention. This can be attributed to the low material cost as well as its low energy consumption. The micromorph solar cell configuration consisting of a top amorphous silicon cell and a bottom microcrystalline silicon cell has proved to be one of the promising approaches in thin-film silicon solar cells. The importance of the microcrystalline silicon cell lies in its higher performance in absorption of photons in the long wavelength region of the spectrum. In this thesis we made use of the ASA simulator to study microcrystalline silicon solar cells. We started by carrying out the calibration process of a model microcrystalline solar cell to be used for the simulations. A sensitivity study was carried out for both optical and electrical parameters of the solar cell. The study showed that the RMS roughness of the interfaces of the solar cell especially the TCO-p interface significantly affect the solar cell performance. It is shown in this work that parasitic absorption in the front TCO and the p-layer can be enormous and reduce the overall absorption in the absorber layer. The electrical properties of the solar cell were also studied, showing the sensitivity of the solar cells external parameters (short circuit current density, open circuit voltage, fill factor) as well as the solar cell efficiency to properties such as the mobility gap, layer thickness, activation energy, etc. The effect of a buffer layer between the p-i interface and graded absorber layer on the open circuit voltage was investigated. The result shows that the external parameters of the solar cell are improve upon by implementing the i-layer grading. The Voc also increases with aSi:C buffer layer inserted between p- and i-layer. The Jsc and the fill factor and not affected much. The use of modeling and simulation is a very useful tool in the study of solar cells. This work shows that the feature is bright with regards to what can be achieved in the optimization of microcrystalline silicon solar cells.