ANALYSIS OF BURIED CONTACT SOLAR-CELLS AND SOME RULES FOR THEIR OPTIMUM DESIGN

One of the most promising structures for solar cells is the Buried Contact Solar Cell (BCSC), because it offers the possibility of production at low cost, at the same time that it allows the combination of several high efficiency concepts without any design compromise as occurs in conventional cells. Therefore, there is a growing interest for such kind of solar cells. Unfortunately, this structure poses new problems for its design since the buried contact will cause two-dimensional carrier how effects under both light and dark current conditions. However, as we describe in this paper, it is possible to make a simple analysis of the conversion efficiency as a function of the buried contact depth in the BCSC cell. In this article we will show that the efficiency is minimum for depths in the range between 50 and 70 mu m when the assumed parameters are typical for silicon solar cells. In addition, we will show that in order to have good performance for these cells, the buried contact depth should be very small (below 5 mu m), or very large (bigger than 150 mu m) instead, but not in-between these values, in order to avoid any efficiency degradation caused by the buried contacts. Finally, we shall show that the efficiency can be better than in conventional cells only when the buried contacts have a large depth, whenever they are designed properly such that they allow additional collection of charge carriers generated by sunlight.