Investigation of laser ablation of silicon nitride passivation with self-doping paste for solar cell contacts

We have fabricated solar cells using a standard POCl₃ process along with a PECVD SiN_x AR coating. In particular, we have also used a self-doping paste with belt furnace firing in conjunction with laser ablation to remove the silicon nitride passivating layer to minimize the metal contact area. Use of laser ablation to create holes in the nitride passivation is coupled with use of a silver self-doping paste to create a selective emitter. Cell results with an efficiency of 13% were obtained. Discussion of the fabrication steps needed and the analysis of the data are given below. The cells suffer from low open circuit voltage as well as modest fill factors. Increased shading losses and unoptimized AR coating limit J_sc. The self-doping paste cells had a very high contact resistance, the root causes of which are discussed.