Cell Processing

Si etch processes are vital steps in Si solar cell manufacturing. They are used for saw damage removal, surface texturing and parasitic junction removal. The next generation of Si solar cells, featuring thinner wafers and passivated rear surface, will pose more stringent demands on those steps. Surface decoupling (achieving different surface treatments on the front and the rear) has to be achieved while minimizing Si consumption. Plasma texturing is an emerging technique that appears very promising in that respect, as efficiencies as high as 17.4 % have been achieved on screenprinted multicrystalline Si solar cells incorporating this process.

Standardized requirements for the quality of PV modules, solar cells and wafers are given in the according IEC norms (e.g., IEC 61215, 61646, and IEC 61730 for modules). However, the manufacturers of cells purchasing wafers and the module manufacturers purchasing cells want information beyond the final check of the product and to monitor each step during the production process to identify harsh handling and/or machine faults at the earliest stage possible. With consequential improvements of the process enabled, continuous improvements in throughput and yield improvement of the factory are likely, also allowing an early feedback on quality issues to the raw material supplier. Furthermore, by knowing all characteristics and factors of the cell and the module, prediction of electrical energy yield during the life cycle of a PV power plant is becoming more accurate and more reliable.

Increasing the efficiency and yield of production line processes forms an integral part of PV manufacturers’ technology roadmaps. For their next generation production lines, non-contact processing equipment is considered essential. This prioritizes laser-based processing, already established at several steps in c-Si and Thin-Film cell manufacturing. This paper summarizes the key issues when using lasers within PV production lines.