Heavily Doped Polysilicon-Contact Solar Cells

We report 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. Compared with BSF and back-ohmic-contact (BOC) control samples, the polysilicon-back solar cells show improvements in red spectral response (RSR) 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) polysilicon, consistent with past findings for bipolar transistors, and for p-type (Si) 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. © 1985 IEEE