The Freudenstadt-based SCHMID group achieved the 20.74% efficiency rate during a simulated production process for the manufacture of PERC solar cells. Schmid explains that the most important features of a PERC solar cell are the passivated selective emitter layer and the backside passivation.
The record efficiency rating was confirmed independently by the ISE CalLab, and SCHMID says it expects an even higher efficiency potential of 21% for its recently-introduced multi busbar interconnection concept with front side metallisation: "This is because SCHOTT Solar has reached an independently confirmed efficiency record of 21% for the first time ever on p-type Cz-Si wafers with industry dimensions of 156mm x 156mm".
According to the company, the effectiveness of the APCVD generated Al2O3 passivation layer is comparable to PECVD coatings but comes without "expensive vacuum technology". Alternative processes like PECVD or ALD machines would cost 3 to 5 times as much, claim SCHMID, meaning that cell manufacturers get an immediate economic solution allowing them to be more competitive.
The process for the Al2O3 backside passivation with the APCVD has been developed by development engineers in SCHMID's own technology center in the company’s Freudenstadt headquarters working together with the University of Konstanz.