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

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. [Display omitted] •Continuous wave laser doping of Si creates SiOxNy which hinders NixSiy formation.•Little NixSiy results in poor mechanical adhesion of plated Ni–Cu contacts.•Chemical removal of SiOxNy results in penetration of the pn-junction by NixSiy.•A deep pn-junction and contact opening by pulsed laser prevents device degradation.