Experimental comparison of light-trapping structures for silicon solar cells

Silicon solar cells and test structures were made with etched V-grooves on both the front and the back. The light trapping in these structures was compared to that of control samples with polished and textured surfaces. It was found, in agreement with theoretical predictions, that the structure in which the grooves on the front and the back are perpendicular showed the greatest degree of light trapping, i.e. absorbed the most light in the near-bandgap region. Furthermore, the V-groove front surface makes possible a reduction in effective shadow loss by allowing reflection of light from the metal grid lines onto the active area; this reduction was measured at 41% in a typical cell. An 0.25 cm² bifacial concentrator cell with a short-circuit current density of 41.5 mA/cm² was made by this method.