Process Development and Control of Contact Firing Processes for High-efficiency Silicon Solar Cells
The Research Project “FEUERDRACHE”
The target of the research project under the management of the Fraunhofer Institute for Solar Energy Systems ISE Freiburg, was the optimisation of the production process for high-efficiency PERC silicon solar cells. For this purpose, an innovative contact firing process together with the associated in-situ process control was to be achieved. In the sub-project of InfraTec, a technology for contactless measurement and monitoring of the wafer temperature in the contacting process was developed to achieve this purpose as an alternative to the previous temperature measurement with thermocouples.
In the project, different thermographic systems were integrated in the contact firing furnace. These were adapted and successfully tested by the use of conventional and innovative beam sources (IR emitters and VCSEL diodes) according to the specific requirements in terms of wavelengths, power densities, high ambient temperature as well as to the different spatial scenarios. The infrared camera ImageIR® 8300 delivered excellent results in the specific application.
Instead of the punctual measurement of the process temperature in the furnace and extensive individual measurements on specially prepared cells, the results of the research project showed that the complete recording of the temperature distribution of the entire wafer surface is possible. Hereby, the process temperature in the "peak zone" can be optimally controlled, the throughput speed increased, and the production costs were reduced as well as simultaneously higher cell efficiency can be achieved.
The research project „Feuerdrache“ was supervised during the period from 01.07.2017 until 30.06.2020 by the project sponsor Jülich (PTJ) under the promotional code 0324205B. The financing of the project was supported on the basis of a resolution of the German Parliament by the Federal Ministry of Economics and Energy.