Strain-engineered performance enhancement in CsSiBr3 solar cells through DFT and SCAPS-1D simulations

Abstract

The development of lead-free absorber materials for photovoltaics is crucial to reconcile high performance with environmental sustainability. In this study, we investigate the inorganic perovskite CsSiBr₃ as a promising alternative, employing density functional theory (DFT) and SCAPS-1D simulations to assess the impact of triaxial strain on its structural, electronic, and photovoltaic properties. Our results reveal that the band gap can be tuned from 0.65 eV (−6 % compressive strain) to 1.35 eV (+6 % tensile strain), enabling a transition from a quasi-metallic to a semiconducting regime. Under tensile strain, enhanced optical absorption and carrier collection are observed, indicating improved potential for photovoltaic applications. Device simulations (FTO/TiO₂/CsSiBr₃/MoO₃/Au) show that the widening of the band gap under strain increases the open-circuit voltage (from 0.63 to 1.01 V) and fill factor (from 83.13 % to 87.88 %), while the short-circuit current density undergoes a gradual decline (from 43.57 to 29.18 mA/cm²). Consequently, the power conversion efficiency (PCE) improves from 23.17 % (unstrained) to approximately 26 % under 6 % tensile strain, a value that, although below the Shockley-Queisser limit (∼33 %), demonstrates the effectiveness of strain engineering for optimizing CsSiBr₃. These findings highlight the potential of this material as a stable, environmentally friendly absorber for next-generation solar cells and pave the way for future experimental validation.