Theoretical Insights of Degenerate ZrS<sub>2</sub> as a New Buffer for Highly Efficient Emerging Thin‐Film Solar Cells
Kaviya Tracy Arockiadoss, Karthick Sekar, Latha Marasamy
Abstract
SnS, Sb 2 Se 3 , Cu 2 SnS 3 , CuSb(S,Se) 2 , and Cu 2 BaSn(S,Se) 4 are emerging as promising light absorbers for thin‐film photovoltaics due to their extraordinary optoelectronic properties. However, improper band alignment with the buffer and large open‐circuit voltage ( V OC ) deficit limits their power conversion efficiencies (PCE). Therefore, finding a suitable buffer that overcomes these obstacles is crucial. Herein, ZrS 2 as an alternative buffer for the aforementioned emerging thin‐film solar cells using SCAPS‐1D is proposed. The important ZrS 2 parameters are optimized, including bandgap, thickness, carrier concentration, and defect density. Interestingly, ZrS 2 behaves as a degenerate semiconductor at carrier concentrations >1E17 cm −3 , improving the conductivity of the solar cells; it also demonstrates a high defect tolerance nature when the defect density lies between 1E12 and 1E18 cm −3 . After ZrS 2 parameters optimization, the built‐in potential of SnS, Sb 2 Se 3 , Cu 2 SnS 3 , CuSb(S,Se) 2 , and Cu 2 BaSn(S,Se) 4 solar cells is enhanced by 0.2, 0.58, 0.05, 0.42, and 0.3 V, respectively, reducing recombination rate. Upon optimizing absorbers parameters, a PCE > 35% for SnS, Sb 2 Se 3 , and CuSb(S,Se) 2 while >32% for Cu 2 SnS 3 and Cu 2 BaSn(S,Se) 4 solar cells is accomplished with low V OC loss (≈0.1 V). The absorbers must have high carrier concentration (1E20 cm −3 ) and low defect density (1E14 cm −3 ) to achieve these PCEs.