Sn(O,S)2 thin films by chemical bath deposition for Cd-free CIGS thin film solar cells

The buffer layers of tin compound semiconductor were deposited on the Cu(In,Ga)Se-2 (CIGS) substrates by chemical bath deposition. Sn(O,S)(2) films were grown in an alkaline ammonia solution by reaction of tin(IV) chloride with thiourea at the bath temperature of 70 degrees C. The smooth and conformal coverage films were achieved on the CIGS substrates with thickness of 20nm. The morphological and chemical properties were evaluated using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). On the other hand, layer thickness of 90nm could be grown in an acidic solution with sodium sulfide (Na2S) within 60min When we applied the Sn compound thin films as the alternative buffers in thin film CIGS solar cells, the efficiency of 9.4% small area cells were achieved. This result provided the potential for the Sn(O,S)(2) films to be used as buffer or window layers in solar cell devices.