Solution-processed ultrathin SnO2 passivation of Absorber/Buffer Heterointerface and Grain Boundaries for High Efficiency Kesterite Cu2ZnSnS4 Solar Cells

The ultrathin SnO 2 film, prepared by the successive ionic layer adsorption and reaction (SILAR) method, was applied between p-type Cu 2 ZnSnS 4 (CZTS) and n-type CdS layers to passivate the interface as well as the top section of CZTS grain boundaries. With the aid of this layer, electric properties have been significantly improved. The device efficiency improved from 6.82% to 8.47%, which is mainly contributed by the boost of fill factor (FF) and open circuit voltage (V oc ). However, the further increase of SnO 2 thickness results in decreased J sc and FF. Kelvin Probe Force Microscopy (KPFM) unveils the passivation of grain boundaries (GBs) of CZTS with the SnO 2 coating. This work shows a new insight into the heterointerface and GBs passivation for high efficiency CZTS solar cells.