Abstract
The design of the optimal efficiency silicon solar cell requires the minimization of several performance-limiting phenomena. In particular, much improvement is necessary to decrease the loss of minority carriers to recombination. Thus, in order to focus our design efforts in the development of an optimal efficiency solar cell it is imperative that we be able to experimentally distinguish and assign values to the different forms of minority carrier recombination in the cell. Recently, B. H. Rose and H. T. Weaver of Sandia National Laboratories have proposed a method to evaluate minority carrier recombination in the back surface field (BSF) solar cell through measurement of the short circuit current and open circuit voltage decay fates. In this thesis, we critically analyze the Rose-Weaver Method. In particular, we investigate the mathematical model formulated by Rose and Weaver to describe the decay of the short circuit current and the open circuit voltage. A study of the model equations reveals that, for even small fluctuations in the experimental measurements, a large variation in the model solutions occurs. Moreover, the solution of the model is shown to rely on extremely accurate (perhaps unobtainably accurate) knowledge of material parameters. To avoid dependence on material parameters, we analyze a second experiment in which the back surface field of the solar cell is removed. However, the model which results from combining this experiment with the original experiment shows an even greater variation of the model solutions to uncertainty in the experimental measurements. In summary, unless we make extremely precise measurements and avoid dependence on imprecisely known material parameters, particularly, n;, the Rose-Weaver Method can lead to radically different descriptions of minority carrier recombination in the solar cell.
Date of this Version
5-1-1985
Comments
MSEE. This thesis has been made possible through the support of Sandia National Laboratories, Document Number 52-5675