First ribbon growth on substrate (RGS) solar cells with selective emitter

Abstract

Ribbon Growth on Substrate (RGS) technology is a cost-effective approach in terms of silicon usage per watt peak. The wafers are cast directly out of the melt onto reusable substrates. This process omits material losses which occur e.g. by wire-sawing in standard blockcast wafering techniques. Also the wafers can be cast at a high production speed in the order of one wafer per second. However, the material suffers from various crystal defects and has grain sizes between 0.1 mm and 1 mm. To develop and adjust new cell designs, we investigate the effect of a selective emitter structure on RGS cells. To realize a selective emitter the etch-back approach is used. It is found that the expected gain of jsc is accompanied by losses in the fill factor. These effects compensate each other in such a way, that no significant increase in solar cell efficiency is observable up. These first experiments with selective emitters on RGS wafers results in efficiencies up to 12.4%.