Pilot-line processing of very large (21 x 21 cm²) and thin mc-Si solar cells

Enlargement of the wafer size from 15.6 x 15.6 cm2 to 21 x 21 cm2 seems to be an effective cost reduction strategy of solar cell production. Especially batch-type production shows a high cost reduction potential. First cell manufacturers are already able to produce multi-crystalline (mc) solar cells based on very large scale (VLS) wafers. But before a mass production is worth, a few challenges like mechanical yield during cell manufacturing and homogeneity over total wafer surface have to be solved. Therefore, more than 100 VLS solar cells with a thickness of max. 240 µm were processed at the pilot-line of the PhotoVoltaic Technology Evaluation Center (PV-TEC) at the Fraunhofer ISE. To transfer the standard solar cell process successfully, a front grid optimisation was carried out, which resulted in cell efficiencies up to 15.2%. Compared with standard 15.6 x 15.6 cm2 mc solar cells the efficiency is in the same range. Furthermore, two mini-modules were successfully produced.