6.56% Efficient CuInS 2 Superstrate Solar Cells Enabled by an Amorphous Tin Oxide Interlayer

Herein, for the first time, we have fabricated superstrate-type CuInS 2 planar heterojunction solar cells configured as FTO/SnO x /CdS/CuInS 2 /Spiro-OMeTAD/Au, in which an amorphous tin oxide (SnO x ) interfacial layer is prepared by a straightforward solution-processing method at low temperatures (≤200 °C), and 2,2′,7,7′-tetrakis( N, N -di- p -methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) is used as a hole-transporting material. It is revealed that the solar cells exhibit a performance that is strongly dependent on the SnO x layer thickness and deliver a peak power conversion efficiency of 6.56% for a 25 nm-thick SnO x layer, which is higher by 78% than that of the control devices without the SnO x interfacial layer. This is attributed to the reduced interfacial charge recombination at the CdS/CuInS 2 interfaces due to the fast extraction of photogenerated electrons from the CdS layer into the SnO x film for collection. This work offers promising interfacial access to efficient CuInS 2 planar heterojunction solar cells.