26-Percent Efficient Point-Junction Concentrator Solar Cells with a Front Metal Grid

Abstract

This paper reports on silicon concentrator cells with point diffusions and metal contacts on both the front and back sides. The design minimizes reflection losses by forming an inverted pyramid topography on the front surface and by shaping the metal grid lines in the form of a triangular ridge. A short-circuit current density of 39.6 mA/ cm2 has been achieved even though the front grid covers 16 percent of the cell's active area of 1.56 cm2. This, together with an open-circuit voltage of 700 mV, has led to an efficiency of 22 percent at one sun, AM1.5 global spectrum. Under direct-spectrum, 8.8-W/cm2, concentrated light, the efficiency is 26 percent. This is the highest ever reported for a silicon cell having a front metal grid. Show more