Effect of Cu content and temperature on the properties of Cu2ZnSnSe4 solar cells

The complexity involved in obtaining pure Kesterite Cu2ZnSnSe4 (CZTSe) thin film primarily arises due to its narrow region of stability, leading to the presence of unavoidable binary selenides of the constituent metals. This study offers an insight on the formation of Cu selenides when the amount of Cu is varied in the precursor from Cu poor to Cu rich. The amount of Cu selenides was found to decrease when the composition of CZTSe absorber approached Cu rich conditions but functional devices were not obtained. Detailed characterizations also showed that the Cu and Sn binary phases were present at the backside interface of CZTSe solar cells. However with an increase in the selenization temperature it was found that the amount of Cu selenides and other secondary phases could be drastically minimized or even eliminated leading to high efficiency devices