"Kesterites combine the low cost of thin film solar cell technologies with extremely low raw material cost. Their main component consists of copper, zinc, tin, and sulfur or selenium, all abundant and low cost elements. Several labs have reported that the loss of tin during preparation limits the ability to control deposition processes. The Laboratory for Photovoltaics has now developed a preparation process that allows controlling the tin loss and has in the first attempt led to record efficiency." (Quoted from article)