High aspect ratio triangular front contacts for solar cells fabricated by string-printing

We are presenting a novel method to fabricate high aspect ratio, triangular cross-section solar cell front contacts, henceforth referred to as string-printing. We optimized string-printing to yield contacts with an aspect ratio larger than 1 and a light redirection efficiency or effective transparency of 67%, thereby mitigating most of the optical losses inherent to flat metallic front grids. In string-printing, a string coated with silver paste approaches a substrate until contact is made. Withdrawing the string then leaves behind silver paste on the substrate. Here, we describe the fabrication method and show initial results including current density-voltage curves of string-printed silicon heterojunction solar cells, as well as the effective transparencies of the contacts. String-printing is a scalable, low-temperature process with high potential to boost commercial solar cell efficiency and lower the module price per Watt.