Self-Patterning Rear Contact Schemes for Silicon Solar Cells

ABSTRACTHigher silicon solar efficiencies are possible if metal contact is made to the cell though openings in a well-passivated surface. Patterning for rear point-contact schemes has typically been achieved using deterministic patterning methods involving either the use of photolithography, laser or inkjet patterning. However, with these approaches it is difficult to achieve cost-effective, high-throughput and robust processing if very small and closely-spaced openings are required. In this paper we review recent progress in the use of self-patterning anodised aluminium oxide layers to both passivate and enable point metal contacts to the rear surface of silicon solar cells. We describe a wet chemical method for anodising aluminium layers thermally-evaporated on the rear surfaces of silicon solar cells, and demonstrate that the layers can result in excellent passivation of the underlying silicon and also enable metal contact to the solar cell. Additionally, we describe how patterning of either the anodic aluminium oxide layer or the source aluminium layer can result in patterns of metallic and dielectric regions on a surface, and how currently-available solar cell electroplating tools can be adapted to achieve anodisation of solar cells at commercial processing throughput rates.