Front and back polysilicon-contacted silicon solar cells

The first use of a (silicon)/ (heavily doped polysilicon)/ (metal) structure to replace the conventional high-low junction (or back-surface-field, BSF) structure of silicon solar cells is reported. Compared with BSF and back-ohmic-contact control samples, the polysilicon-back solar cells show improvements in red spectral response and open-circuit voltage. Measurement reveals that a decrease in effective surface recombination velocity S is responsible for this improvement. Decreased S results for n-type (Si:As) polysilicon, consistent with past findings for bipolar transistors, and for p-type (Si:B) polysilicon, reported here for the first time. Though the present polysilicon-back solar cells are far from optimal, the results suggest a new class of designs for high efficiency silicon solar cells. Detailed technical reasons are advanced to support this view.