Simulations For Front Metallic Electrodes Of Silicon-Based Solar Cells

With the exhaustion of the fossil energy and the increasing environmental problems, solar energy as a reliable, long-term, exhaustless, and environmentally friendly energy source has aroused great interest due to the strong demand for alternatives to fossil fuels. Solar cells are semiconductor devices used to convert solar into electrical energy, which have directly determined the utilization efficiency of solar energy. The conversion efficiency of solar cells not only depends on materials and device structures, but also relies heavily on the front metallic electrode which is used to collect electrons from the semiconductor layer and transfer them to the external load. Considering the solar arrays, even a small optimization over the electrode pattern could bring about considering enhancement of converted energy. In this paper, we propose two simulated models for the front metallic electrodes of solar cells and estimate the strengths and weaknesses for next further optimization by calculating conversion efficiency. The models we proposed own both high accuracy and wide applicability in addition to saving lots of testing cost including time and funds. This paper content arranges as follows:In chapter one, we sketch the general development situation of solar cells and introduce some correlative simulation works on the front electrode of solar cells. Those research works are the reference of our work.In chapter two, we introduce the theoretical basis of our work. Through device structure analysis and equivalent circuit analysis of silicon-based solar cells, we figure out the UI equation of solar cell and explain the constitutions of series resistance. The key to simulation is to solve the series resistance of solar cell.In chapter three, we propose a model to compute the conversion efficiency of silicon-base solar cell with comb-like pattern on its surface. According to the parametric expression deduced from comb-like pattern, we use MATLAB to solve the UI equation to calculate the conversion efficiency. Through the comparison between simulated results and experimental results, we show the extreme veracity of our model. Further more, by sweeping the geometric dimension parameter of comb-like pattern, we demonstrate the very fine line width(~10um) for comb-like pattern might not lead to ideal conversion efficiency enhancement.In chapter four, we build a two-dimensional(2D) numerical calculation model to simulate the front metallic electrode using Finite Element Method(FEM). Conventional algorithm to conversion efficiency of silicon-based solar cells is to divide the cell surface into large number of elementary sub cells, which are represented by an equivalent electric circuit model and solved with circuit simulator. Usually, the circuit will contain the complicated resistive components if the front metallic electrode design is quite complex. It poses to designers a difficult and time-consuming task of figuring out the equivalent resistors of the elaborated front electrode design, which might lead to the inaccurate output results. In this paper, we propose a 2D model to simulate various front electrode designs with considering the full complexity of electrodes on the front surface of solar cell. Besides, the distributed maps of potential, resistance losses and current direction could be figured out for next further optimization. The feasibility and the accuracy of our model are demonstrated by comparing the simulated results with the testing ones.The researches in this paper aim at putting forward computation ideas and methods of simulating the front electrodes of silicon-based solar cells. It would be important for further studying solar cells to provide a new assistive tool to optimize or develop electrode patterns.