Design Simulation of Chalcogenide Absorber‐Based Heterojunction Solar Cell Yielding Manifold Enhancement in Efficiency

Abstract

A large efficiency improvement, ≈4.5 times, in a solar cell based on earth‐abundant low‐cost SnS absorber with configuration glass/Mo/SnS/CdS/i‐ZnO/AZO/Al is reported in sharp contrast to prior experimental reports in the literature. Efficiency enhancement is attributed to tailored design at the absorber/buffer interface implemented via two‐step design modification vis‐à‐vis experimental benchmark. Design tailoring using simulation comprises substitution of sulfur composition in SnS by Se followed by replacing CdS buffer layer with wide bandgap, nontoxic Zn (O, S). The effect of sulfur composition variation by Se (i.e., SnS1−xSex) indicates an optimal Se mole fraction (x = 0.4) exhibiting maximum efficiency. In addition, optimization of the thickness, carrier density, and bulk defect density of the SnS1−xSex absorber result in an improved design. Replacing CdS buffer layer by ZnO1−ySy in SnS absorber‐based solar cell results in substantial improvement in device parameters; open circuit voltage (VOC) of ≈86% and current density (JSC) of ≈78% due to optimal band alignment at the SnS1−xSex/ZnO1−ySy heterojunction. It occurs when the sulfur mole fraction is 60% in the absorber layer and 70% in the buffer layer causing efficiency to rise to ≈17.87%. An optimal design comprising all the parameters including metal back contact work function, series and shunt resistance deliver an efficiency of ≈19.2%.