SCAPS-1D study on the design and performance optimization of Sr3NCl3 solar cell: Assessing the significance of copper oxide (Cu2O) and copper(I) thiocyanate (CuSCN) as hole transport layers

Abstract

Strontium-Nitride-Chloride (Sr₃NCl₃) is a novel lead (Pb)-free, stable absorber material with direct band gap (1.75 eV) that is particularly well suited as a top sub-cell in tandem structures because of its favourable semiconducting properties and hence its potential as an absorber in single junction devices needs to be evaluated. Using SCAPS-1D, we have optimized a Sr₃NCl₃ active layer (ActL) based solar cell by tuning the ActL thickness, defect density and interface properties in FTO (fluorine doped tin oxide)/electron transport layer (ETL)/Sr₃NCl₃ (ActL)/hole transport layer (HTL)/Metal based single junction configuration. Tin sulfide (SnS₂) is used as an ETL and copper based HTLs such as copper oxide (Cu₂O) and copper(I) thiocyanate (CuSCN) are investigated as novel HTLs to optimize the performance of Sr₃NCl₃ solar cells. Simulations for different back metal contacts (Ag, C, Au, Pt and Se) are investigated in with and without HTL devices. Energy band offset and capacitance-voltage analysis reveal the role of back contacts and HTLs in enhancing built-in voltage (V_bi), short circuit current density (J_sc) and open-circuit voltage (V_oc), results in PCE improvement. Sr₃NCl₃ solar cell has achieved PCE ∼23.55 % with V_oc = 1.39 V, J_sc = 19.30 mA cm⁻², and fill factor (FF) = 87.54 %, comparable to that of state-of-the-art Pb-free photovoltaics and found to be within the Shockley-Queisser limits. Without HTL as well, Se metal contact device, maintains comparable high PCE, demonstrating the robustness and strong potential of Sr₃NCl₃ for further exploration. This study places Sr₃NCl₃ to be among the competitive Pb-free absorbers, offering a wide-bandgap alternative for next-generation photovoltaics.