DescriptionThe development of affordable, inexhaustible and clean solar energy technologies will have huge long term benefits, and the solar cell lies at the heart of this technology, which converts the incident sun light into electric current. During the last years the performance of bulk hetrojunction solar cells has been improved significantly making them a viable option for future generation solar cells. For a large-scale application of this technology further improvements are required. In this thesis, we explore the means to improve the efficiency of organic solar cells by studying the one dimensional drift diffusion equations and understanding the parameters which play a significant role in the operations of these devices. After identifying the physical parameters, a state space technique is applied and the nonlinear model is developed which is both time and space varying. Then, two sub models are derived - one by freezing space and another by freezing time. Both models are nonlinear. We perform linearization of the nonlinear model around a nominal operating point for the purpose of designing linearized optimal controller. The controllers obtained are applied to the nonlinear solar cell model. As the parameters are numerically very large in range, we performed scaling and derived a scaled down model. The internal stability of both the models is checked and an optimal controller is developed around the nominal point with the objective to maintain a constant number of electrons and holes which in turn directly affects the output current of the solar cell. This steady state constant values can ensure desired charge separation which sweep towards the cathode and anode before they exit the device. In the event of high intensity of sunlight this steady state values will help overcome the space charge effect which is an important factor in organic cells. The model is also subjected to the Turing instability test for a reaction diffusion system to investigate and detect the presence of Turing patterns in the drift-diffusion model of the organic solar cell.