The SCHMID Group (Freudenstadt, Germany) expects several orders in 2013 for its APCVD system for industrial mass production of high efficiency cells on p-type as well as n-type Cz base material. The sales of two machines at the beginning of the year to a cell manufacturer and to an institute prove the growing interest of a broad industry and research market in APCVD production technology. The two machines are used in developing PERC , n-type PERL and PERT cell concepts. Since years nearly one hundred APCVDs of SCHMID Thermal Systems Inc. (Watsonville, USA) are successfully in the field, e.g. for manufacturing doped glasses in the semiconductors industry or for the fabrication of high efficiency solar cells.
Dr. Christian Buchner, head of SCHMID’s PV-division, explains the optimistic outlook: “If demand for solar cells is rising in the mid-term globally and explosively as industry experts predict, cell manufacturers cannot come up with technology from the year 2011. The right time for upgrading production lines for the fabrication of PERC cells is basically now. When companies decide on equipment, SCHMID is ahead as it is the only PV supplier with a complete process and the necessary equipment out of one hand.”
SCHMID’s PERC portfolio comprises all steps from wet chemical rear side cleaning over APCVD deposition up to rear side laser opening. All systems are easy to integrate into existing production lines and offer the lowest cost of ownership at the market. According to SCHMID calculations the deposition of aluminum oxide and capping layers with APCVD saves about 40-50% costs compared to alternative ALD processes or PECVD processes.
PERC cells are made out of crystalline silicon. Rear side passivation requires the deposition of an aluminum oxide layer and two capping layers onto the base material. The cells reach an efficiency of at least 20% with the SCHMID process.
SCHMID’s APCVD is capable not only of passivation but also of high quality and low cost deposition of PSG and BSG for doping. BSG is interesting for manufacturing n-type cells which show no light induced degradation and have the potential for high efficiencies.