High efficiency, large-area p+- n- n+ silicon solar cells

Abstract

The work reports the development of high-efficiency, large-area, preferentially current-generating p +- n- n + silicon solar cells. The distinctive trait of the developed cells is their extremely high value of the short-circuit current density J sc under AM1 conditions (100 mW/cm 2 insolation). Two main factors had shaped the unique features of these large-area (17.2 cm 2) cells. One of the factors is the peculiar impurity profile of the p +- n junction with a depth of x j = 0.15–0.25 μm, obtained through adequate technological means. The second factor is a novel, optimized front grid metallization pattern, which reduces the areal inhomogeneities typical of large-area devices. The combined action of these factors has reduced the coverage ratio to about 5.6% and confined the series resistance R S to 60–100 mΩ range. The conversion efficiency of cells exceeds 17%. The results of this work were obtained in industrial environment, not laboratory conditions. It is noteworthy that none of the usual refinements (double AR layer, textured surface, etc.) were used in the fabrication process. Thus, this work shows clearly that a simple, but adequately designed/processed large-area p +- n- n + cell could possess parameters similar or even superior to those of sophisticated laboratory samples elaborated on small (2 × 2 cm) silicon chips.