Numerical design and performance optimization of emerging SrZrS3-Based solar cells integrated with ZrS2 and CZTS transport layers

Chalcogenide perovskites are emerging as stable, lead-free alternatives for photovoltaics, with SrZrS3 highlighted as a promising absorber due to its favorable optoelectronic properties. This study introduces the novel integration of Zirconium Disulfide (ZrS₂) as an electron transport layer (ETL) with SrZrS₃ through SCAPS-1D numerical simulations. This enables a lead-free chalcogenide perovskite solar cell architecture that leverages quasi-2D structure of ZrS2 with tunable bandgap (~1.2-2.2 eV), and favourable band alignment to drive efficient charge extraction with minimal interfacial recombination. Incorporating Copper-Zinc-Tin-Sulfide (CZTS) as hole transport layer (HTL) improves carrier selectivity and device stability. With gold back-contact architecture (PCE 12.46%) as reference, systematic optimization of interfacial, structural, and electronic parameters significantly enhanced efficiency, while inclusion of resistive losses and temperature effects ensures practical relevance. Real-world applicability was ensured by accounting for interfacial defects at ETL/absorber and absorber/HTL junctions, with influence of series and shunt resistances. An optimized Ni back-contacted architecture with a 2.5 μm highly doped absorber, reduced defects, and tailored interfaces delivers VOC ~1.297 V, JSC ~ 25.64 mA·cm⁻², FF ~ 88.13%, and an exceptional PCE of ~ 29.24%. These findings highlight how interface engineering and material design drive the advancement of lead-free, all-inorganic chalcogenide perovskite solar cells, charting a compelling route toward sustainable, high-efficiency photovoltaics.