Photovoltaics of CZTS

Abstract

Cu2ZnSnS4-based (CZTS) solar cells are emerging ones and attracting much attention from the viewpoints of using earth abundant elements. CZTS is quaternary I2-II-IV-VI6 compounds, and they are derivative of Cu(In,Ga)Se2 (CIGS) which have already commercialized. In this chapter the similarities and differences between CZTS and CIGS are comprehensively described, which is one of the features of this chapter. Annual production in several TW scale will be expected in 2030, and the scale corresponds to tens-times of current production compared to current 0.1 TW production. In this situation, a viewpoint of resources must be taken into account as well as cost of solar cells. CZTS are a good candidate to fulfill the requirement. Moreover, CZTS solar cells are suitable for tandem solar cells to meet the requirement in resources. Currently, most serious drawbacks of CZTS solar cells is low Voc, that is, large Voc deficit, and the maximum conversion efficiency is 12.6%, which is much smaller compared to that of CIGS and CdTe solar cells. In this chapter, the origin of the low Voc, and trial to overcome the problems are introduced and discussed.