Kelvin probe microscopic studies on grain boundaries of Cu(In, Ga)Se2 and Cu2ZnSnSe4 thin-films grown by co-evaporation methods

Cu₂ZnSnSe₄ (CZTSe) thin-films is a promising candidate for absorber layer as an alternative to Cu(In, Ga)Se₂ (CIGS) solar cells. However, they have been recorded lower efficiency than that of CIGS until now. In CIGS, local electrical property is an important issue for high efficiency such as Na interstitial in the grain boundaries (GBs). Therefore, difference between CIGS with CZTSe in local electrical property can be one of the clues for explaining lower efficiency of CZTSe thin-film solar cells than CIGS. We studied local surface potential using Kelvin probe force microscopy (KPFM) around GBs. The results reveal difference of electron-hole transport behavior on both thin-films at GBs. Eventually, we can understand relation between solar cell efficiency and local electrical property.