Improving Long-Term Stability of Kesterite Thin-Film Solar Cells with Oxide/Metal/Oxide Multilayered Transparent Conducting Electrodes

The long-term stability of kesterite Cu2ZnSn(S,Se)(4) (CZTSSe) thin-film solar cells (TFSCs) is crucial for the sustainable mass production of photovoltaic systems. Herein, the improved long-term stability of CZTSSe TFSCs with an oxide/metal/oxide (OMO)-based transparent conducting electrodes (TCEs), i.e., ZnO-based oxide/Ag/Al-doped ZnO (AZO), and post heating treatment is reported. The effect of the structural, optical, and electrical properties of the OMO TCEs prepared with various bottom oxide materials on the device performance of the CZTSSe TFSCs is systematically investigated. The CZTSSe TFSCs with Ga-doped ZnO containing OMO TCEs show excellent long-term stability with only <1% and <20% power conversion efficiency (PCE) losses, whereas for the TFSCs with conventional AZO TCEs, 12% and 69% PCE losses are observed after 5 and 10 months, respectively, without encapsulation and air atmosphere. Detailed analyses reveal that Ag-doped ZnO formed at the bottom oxide/Ag interface in OMO TCEs passivates the interface. Accordingly, a passivation mechanism for the Ag-doped ZnO interfacial layer in the OMO TCEs is demonstrated. Herein, a new pathway to improve the long-term stability of CZTSSe TFSCs without encapsulation and under air atmosphere is offered.