Overcoming electrical and mechanical challenges of continuous wave laser processing for Ni–Cu plated solar cells

Abstract

Continuous wave laser processes used to create solar cells with selective emitter and plated Ni–Cu front contacts are a widely discussed topic. Particularly low adhesion of the front metal contact has been identified as a serious challenge. In this work a detailed surface characterization of laser doped and patterned front sides of solar cells shows that formation of silicon oxynitride hinders nickel silicide formation and reduces contact adhesion of Ni–Cu plated contacts. In order to overcome the observed tradeoff between metal contact adhesion and penetration of the pn-junction, this paper presents a novel process sequence based on the formation of a deep selective emitter using a green continuous waver laser and subsequent patterning of the dielectric using a nanosecond-pulsed laser.