Advances in CZTSSe Thin-Film Solar Cells: Materials Engineering and Device Optimization

Copper–zinc–tin–sulfide–selenide (CZTSSe) thin-film solar cells have emerged as one of the most promising Earth-abundant, non-toxic alternatives to conventional chalcogenide absorbers. However, their power conversion efficiencies are still limited by intrinsic defects, interfacial recombination, and sub-optimal band alignment. This presentation reviews recent advances in materials engineering and device optimization aimed at overcoming these limitations. Key progress includes compositionally graded CZTSSe absorbers for enhanced carrier collection, alkali metal treatments to suppress deep defects, and innovative buffer layer systems that improve band alignment while minimizing interface recombination. Additionally, improved crystallization strategies—such as controlled selenization/sulfurization pathways and precursor stacking designs—have led to larger grain sizes and reduced disorder. On the device level, optimization of back-contact engineering, passivation schemes, and advanced optical management has contributed to higher open-circuit voltage and overall efficiency gains. Together, these developments highlight a clear pathway toward achieving high-performance CZTSSe solar cells and accelerate their potential for scalable, low-cost photovoltaic deployment.