The effects of high level injection on the performance of high intensity, high efficiency silicon solar cells

SCAP2D, a two-dimensional numerical code for silicon solar cells, was used to explore the mechanisms controlling performance in high-efficiency cells, focusing on the point contact cell for which record efficiencies have been reported. It is demonstrated that accurate predictions of the intensity dependence of the short circuit current and open-circuit voltage of these cells can be obtained by the inclusion of free-carrier bandgap narrowing in the base and the reduction of the minority-carrier mobility in the base to approximately one-half the conventional value of D.M. Caughy and R.E. Thomas (1977). In addition, the value for the ambipolar Auger coefficient obtained by J. Dziewior and W. Schmid (1977) is retained, despite measurements which suggest it may be a factor of four larger. Bandgap narrowing due to high-injection conditions in the base may be another important limiting factor in silicon solar cells.