Verified by the Fraunhofer Institute for Solar Energy Systems ISE, Zentrum für Sonnenenergie (ZSW) has achieved 10.3% conversion efficiency (cell; 0.5cm2) with Kesterite absorber material using a printing process rather than by conventional low temperature vacuum techniques.
“The new compound is similar to CIGS, however, instead of indium and gallium, it contains the abundantly available elements tin and zinc” said, Prof. Dr. Michael Powalla, ZSW board member and head of the Photovoltaics Division. “During the Kesterite solar cell manufacturing process, substrate glass is coated with a non-toxic ink solution containing the preferred elements – without requiring any complex vacuum technology.”
The resulting precursor layer is subsequently selenised in a heating process, with the remaining production process using the same methods as the related CIGS processes. However, ZSW noted that Kesterite cells were not yet ready for commercialisation,
The use of zinc and tin as a replacement for In/Ga, primarily on a cost basis has been of interest for over a decade. The copper zinc tin sulfide (CZTS) world record is currently held by IBM at 11.1%.
ZSW said that it broke through the 10% efficiency threshold for Kesterite solar cells in October, but using printing processes that were said to be simpler and at a lower cost to the current record.
“These fundamental findings are absolutely essential for any technological progress in terms of sustainability, more efficient manufacturing processes and a reduction in costs,” added Powalla.