Investigation of micro-electrical properties of Cu2ZnSnSe4 thin films using scanning probe microscopy

We report on a local potential and resistance mapping of Cu2ZnSnSe4 (CZTSe) films using nm-resolution electrical scanning probe microscopies of scanning Kelvin probe force microscopy and scanning spreading resistance microscopy. We have conducted a comparative study with high-performance Cu2(In,Ga)Se2 (CIGSe) film. Both CZTSe and CIGSe were deposited by co-evaporation of elements in vacuum. The results show that the microelectrical properties of the two polycrystalline materials are similar-higher potential and lower resistance on the grain boundaries (GBs) than on grain surfaces-suggesting inverted GB carrier polarity of these films. The consistent GB properties in contrast to the large difference in photovoltaic output of the two materials suggest that factors other than the GBs are responsible for the low photovoltaic output of CZTSe device. •We found a higher potential on grain boundaries than on grain surface of CZTSe.•We found an electrical conduction channel along the grain boundaries.•We proposed an inverted grain boundary polarity based on our experimental finding.•The origination of low performance of CZTSe cell from grain boundaries is excluded.•We found similar microelectrical properties of CZTSe and CIGSe thin films.