Simulation-Based Analysis Of Multilayer Czts Heterojunction Solar Cells Using Scaps-1d

Abstract

Copper zinc tin sulphide (Cu₂ZnSnS₄, CZTS) has emerged as one of the most promising earth-abundant, non-toxic 
absorber materials for thin-film heterojunction photovoltaics, offering a credible route beyond the scarcity and 
toxicity constraints of CIGS and CdTe. This paper presents an empirical, data-driven numerical study of a 
multilayer CZTS heterojunction solar cell modelled and optimized using the one-dimensional Solar Cell 
Capacitance Simulator (SCAPS-1D). A baseline architecture of SnO₂:F / i-ZnO / n-CdS / p-CZTS / Mo was 
constructed, and the coupled Poisson and carrier-continuity equations were solved under AM1.5G illumination 
at 300 K. A systematic parametric sweep was carried out over absorber thickness (0.5-4.0 µm), acceptor doping 
density (10¹⁴-10¹⁹ cm⁻³), bulk defect density (10¹³-10¹⁸ cm⁻³), buffer-layer thickness, absorber band gap and 
operating temperature (280-400 K). Five structured datasets and seven analytical charts quantify the influence 
of each variable on open-circuit voltage (Vₒᴄ), short-circuit current density (Jₓᴄ), fill factor (FF) and power 
conversion efficiency (PCE). The optimized device achieved a simulated efficiency of 20.9%, with Vₒᴄ = 0.842 V, 
Jₓᴄ = 24.8 mA/cm² and FF = 74.8%, obtained for a 3 µm absorber doped at 5×10¹⁷ cm⁻³ with a defect density 
below 10¹⁵ cm⁻³. Bulk defect density and absorber/buffer band alignment were identified as the dominant 
efficiency-limiting factors, whereas thickness beyond 3 µm produced diminishing returns. The results establish 
quantitative design windows for high-performance CZTS devices and are benchmarked against reported 
experimental and simulation studies, confirming that defect engineering and interface optimization are decisive 
for closing the persistent gap between theoretical and practical CZTS efficiency.