Effect of SnS buffer layer on solution process prepared Cu₂ZnSnS₄ solar cells

The effects of SnS buffer layers on the interfacial morphology, electrical model, and photovoltaic properties of solution-prepared CZTS devices were examined. Two SnS buffer layers were prepared and compared. The CZTS device that was fabricated on the as-coated SnS had many interfacial voids. By contrast, the annealed SnS layer markedly improved the CZTS quality by eliminating the voids at the CZTS-MoS₂ interface. An additional capacitance-resistance circuit in parallel that was responsible for the interfacial defects was required to fit the admittance spectrum of the CZTS device prepared on the as-coated SnS. The efficiency of the CZTS solar cell prepared on the annealed SnS was as high as 8.8%, open-circuit voltage was 570 mV, short-circuit current was 24.08 mA/cm², and fill factor was 64.5%. The open-circuit voltages and fill factor increased 43% and 72%, respectively, when the interlayer changed from the as-coated SnS to the annealed SnS.