Back Contact Plasma Treatment Enables 14.5% Efficient Solution-Processed CuIn(S,Se)2 Solar Cells

Solution-processed chalcopyrite thin film solar cells have made great progress but still lag behind the vacuum-based ones due to inferior absorber quality and non-ideal interfaces. Here, plasma treatment of the molybdenum (Mo) substrate is reported to modify the back interface and improve the efficiency of solution-processed copper indium sulfoselenide (CuIn(S,Se) 2 , CISSe) solar cells. The results show plasma treatment oxides the surface Mo/MoO 2 to high oxidation oxides MoO 3-x (0 ≤ x < 1). The higher surface polarity greatly improves the wettability of the substrate to the precursor solution and results in formation of more compact and uniform precursor film, which grows to void-free larger grains absorber film with better adhesion to the substrate. In addition, the much higher chemical stability of MoO 3-x than Mo significantly reduces the thickness of high resistive MoSe 2 layer. The improved absorber quality and back interface property decreases charge carrier recombination in the absorber and back contact interface, resulting in 14.53% efficiency solution-processed CISSe solar cell, which is improved by 13% compared to device without plasma treatment.