FINALE – Development of Industrial Printing Processes for the Production of Ultra-Fine Line Contacts for Highly Efficient Silicon Solar Cells

Today's research in the field of silicon solar cell technology focuses on the targeted new and further development of individual processes with the aim of increasing solar cell efficiency and reducing process costs. The research project outlined starts right here. It is planned to significantly improve the front side metallization process as a key technology for the production of silicon solar cells. To this end, the screen printing technology established on the market is to be addressed. The technological limits of the printing process and the associated components are to be shifted in the direction of narrower contact widths (<20µm) with sufficient contact height. At the same time, the process costs in EUR/Wp are to be reduced.

The overall project aim is the development of a screen printing process for the realization of contact widths below 20µm with sufficient contact height on mono- and multicrystalline silicon solar cells in an industrial environment. Peak values of 15µm contact width should be demonstrated in the laboratory. In addition to experimental work on printing parameter optimization, the development of a model for the theoretical description of the printing process is also planned. This should support the identification and optimization of central influencing factors in the printing process. The efficiency level of the baseline process in the PV-TEC – Photovoltaic Technology Evaluation Center of Fraunhofer ISE is to be increased by at least 2% in relative terms. Furthermore, the silver utilization in the screen printing process is to be improved by realizing a more homogeneous contact geometry. The contact geometry of the reference technology dispensing serves as target value here. In the field of material and component development, the primary goal is to develop printing forms that allow opening widths of less than 15µm and simultaneously stable printing processes in an industrial environment. The adaptation and optimization of the printing plate manufacturing process, but also of the screen mesh and emulsions, plays a central role in this. The interaction between the substrate surface (texture, coating) and the print result is also the focus of the project. One goal of the project is therefore to build up interdisciplinary process understanding and to develop texture processes with regard to an improvement of the contact geometry. The reduction of process costs in €/Wp is another central goal of the project, which is continuously monitored.

The reduction of the contact finger width to less than 20µm, which is the goal of the project, represents an important milestone in the realization of solar cell efficiencies of about 20%/22% for industrial multi- and monocrystalline p-type solar cells. Based on results from ongoing research projects at ISE (e. g. CUT-A), solar cell efficiencies are to be achieved in this area.