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/cm(2), 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.