Solution-processed Ultrathin SnO2 Passivation of Absorber/Buffer Heterointerface and Grain Boundaries for High Efficiency Kesterite Cu2ZnSnS4 Solar Cells
Heng Sun1, Kaiwen Sun1, Jialiang Huang1, Chang Yan1, Fangyang Liu1, Jongsung Park1, Aobo Pu1, John Stride2, Martin Green1, Xiaojing Hao1
1School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia, Sydney, Australia
/2School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia, Sydney, Australia

The ultrathin SnO2 film, prepared by the successive ionic layer adsorption and reaction (SILAR) method, was applied between p-type Cu2ZnSnS4 (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 (Voc). Furthermore, TEM results unveils the decrease of CdS thickness growing on SnO2 layer, leading to a stronger blue response observed from quantum efficiency profile without any sacrifice of electric parameters. KPFM results exhibit the band bending alteration from downward to upward, indicating the grain boundaries passivation. This work shows a new insight into the heterointerface passivation, shunt-blocking and interface band alignment for high efficiency CZTS solar cells. 

Area: Sub-Area 2.2: Contacts, Windows, Buffers, Substrates and Superstrates, Monolithic Integration, and Interfaces