PECVD SiN(x) Induced Hydrogen Passivation in String Ribbon Silicon

Abstract

To improve the bulk minority carrier lifetime in String Ribbon silicon, SiN(x) induced defect passivation during a post deposition anneal is investigated. Our results indicate that SiN(x) induced hydrogen passivation is very effective when the SiN(x) film is annealed in conjunction with a screen-printed AI layer on the back. In addition, it is found that controlled rapid cooling can be used to enhance the defect passivation process. A model is proposed which relates the high temperature passivation to the release of hydrogen from the SiN(x) film, the injection of vacancies from backside AI alloying, and the retention of hydrogen at defect sites. High efficiency screen-printed String Ribbon solar cells (>14.5%) are fabricated utilizing the simultaneous SiN(x)/AI anneal in a belt furnace for hydrogenation and AI-BSF formation, followed by RTP firing of screen-printed contacts to improve the retention of hydrogen at defects.