GRID METALLIZATION AND ANTIREFLECTION COATING OPTIMIZATION FOR CONCENTRATOR AND ONE-SUN PHOTOVOLTAIC SOLAR-CELLS

In photovoltaic (PV) solar cell research, often the mechanisms of junction formation are studied intensively, while the design of the grid and the antireflection coating (ARC) are somewhat neglected. This is usually because, at the research stage, fundamental information about the junction parameters of novel device materials is more essential than the need to produce high-efficiency devices. Additionally, the equipment and expertise necessary to enable state-of-the-art processing is relatively specialized and often not available to the PV researcher. Nevertheless, during the past few years, many PV research technologies have begun to incorporate optimally designed ARCs and very high-quality metallization, involving processes more typically associated with the micoelectronics industry. Partly because of this, significant improvements in conversion efficiencies have been reported in several key solar cell material systems. In this paper, the models and techniques necessary to design and optimize metal contacts and ARCs for PV solar cells are reviewed and discussed. Additionally, similarities and differences between grid metallizations of cells used under optical concentration and one sun are identified. Through these discussions, the advantages of several recently developed metallization and ARC techniques are reviewed, including very-fine linewidth, buried-contact metallizations, metallizations typically used in the thin-film solar cell industry, and short-circuit current contour modeling for ARC optimization.