An Investigation of the Mechanisms of Light-Induced Nickel Plating on P-type Silicon Substrates

In the process of silicon solar cell production, the fabrication of plated Ni/Cu contacts is regarded as the next generation of metallization processes and has the potential to replace the screen-printing technology. In this paper, we discuss the mechanisms of Light-Induced Nickel Plating (LINP) on semiconductors, which can be applied for Ni/Cu metallization. Our experiments show that when a p- type silicon with or without n/p structure, which has been previously subjected to aluminum metallization on the back, is immersed in a plating bath, metal ions are reduced on the front surface of the semiconductor as soon as illumination starts. The results demonstrate that the mechanisms of light- induced nickel plating are not entirely due to the potential difference induced inside the n/p junction of the semiconductors, as stated by other authors. The main deposition principle may be related to the potential differences separately induced on the metal/solution interface, as well as on the semiconductor/solution interface under thermal equilibrium. To the best of our knowledge this has not yet been mentioned in the literature related to plating. This study discusses the techniques and methods developed to overcome the current shortcomings with electroless plating and electroplating in the solar cell process. Furthermore, the nickel films formed by LINP in a fast and simple process, were analyzed using SEM as well as XPS and shown to display uniform metal surfaces and high intrinsic quality.