Low Surface Recombination in Silicon-Heterojunction Solar Cells With Rear Laser-Fired Contacts From Aluminum Foils

In this study, an approach to create laser-fired contacts from aluminum foils is studied on p-type silicon-heterojunction solar cells. This alternative approach consists of the use of aluminum foils instead of evaporated layers as a metal source and rear electrode for the laser-firing process. A q-switched infrared laser (1064 nm) was employed to create the local point contacts. Quasi-steady-state photoconductance measurements evidenced a limited degradation in the surface passivation quality during the laser-firing process. Heterojunction solar cells fabricated with these rear contacts reached a best conversion efficiency of 18% with a remarkable open-circuit voltage of 690 mV. These values were very close to those of reference devices fabricated with evaporated aluminum layers. This result suggests a similar effect on the rear surface passivation by both contact strategies. However, external quantum efficiency curves revealed a better response from devices with a rear aluminum foil in the near infrared. Optical measurements indicate that this effect can be related to a higher internal reflection at the back surface. Consequently, laser-fired contacts from aluminum foils appear to be a fast and convenient solution for the rear contact of high-efficiency silicon solar cells.