SnS-induced element diffusion Simultaneous optimization of interface and bulk defects in High-Efficiency CZTSSe solar cells

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High-quality interfacial contact and absorber are significant for high-efficiency Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells. With this in mind, the paper puts forward the idea of using a sputtering SnS interlayer at the CZTSSe/Mo interface. The high-temperature decomposition of SnS allowed for the compensation of S and Sn elements in the absorber, as well as induced the redistribution of Na and Cu elements. The diffusion of Na element to the absorber optimizes the crystal quality and improves the interface contact, and the Cu-poor absorber reduces the concentration of CuZn defects. Introducing the SnS-10 interlayer significantly reduces the charge loss, bulk and interface recombination of the device, leading to further improvements in the open-circuit voltage (VOC), short-circuit current density (JSC), and filling factor (FF). Finally, the power conversion efficiency (PCE) of CZTSSe thin film solar cells increased from 8.92 % to 10.49 %, in which the contribution rates of VOC, JSC, and FF to PCE were 27.12 %, 32.33 %, and 40.55 %, respectively. The most significant contribution of the electrical parameters to the PCE was the reverse saturation current density (J0). This finding provides an effective solution to obtain a high-quality interface and absorber, effectively restraining carrier recombination.