First-principles investigation of Pd-based Kesterites for optoelectronic and photovoltaic applications

In this article, we report a first-principles study of the structural, electronic, optical and photovoltaic properties of the earth abundant quaternary Kesterites Cu ₂ PdSnSe ₂ (CPTSe) and Cu ₂ PdSnS ₄ (CPTS). Electronic structure calculations were performed using density functional theory within the full-potential linearized augmented plane wave (FP-LAPW) method. The generalized gradient approximation (GGA) and Hubbard U correction (GGA+U) along with mBJ (TB-mBJ+U) were employed to accurately account for exchange-correlation effects and electrons localization. The calculated band structures revealed that both materials are direct band gap semiconductors with gaps of 1.11 eV (CPTSe) and 1.40 eV (CPTS). The density of states (DOS) shows that the valence band maximum is dominated by Cu-3d, S/Se-p, while the conduction band minimum is primarily composed of Sn-p, Sn-s and Se-p orbital, further the inclusion of Hubbard potential U shifts the localized states below the Fermi level and improving electronic stability. Optical calculations indicate strong visible light absorption (>10 ⁴ cm ^-1) , high dielectric constants and favorable refractive indices, demonstrating efficient light harvesting and low optical losses. Device simulations of the (FTO/WS ₂ /CPT(Se/S)/Spiro-MeOTAD/Mo) architecture were performed using SCAPS-1D. The CPTSe/CPTS based device achieve an open circuit voltage (V _oc ) of 0.95/1.34 V, a high short-circuit current density (J _sc ) of 25.05/15.58 mAcm ^-2 and a fill factor (FF) 0f 86.21/87.82 %, resulting in a power conversion efficiency (PCE) of 20.61/18.34 %. The enhanced performance is attributed to reduce antisite defects, improved cation ordering and optimized alignment. These results established Pd-based Kesterites as promising sustainable absorber materials for high efficient photovoltaic applications.