Enhanced structural stability and optoelectronic properties of lead-free α-phase CsSnI3 perovskite via Zn and Cu doping
Ismail Benaicha, S. Amraoui, J. Mhalla, Youness Ait Alla, Hafsa Diyagh, M. Simassa, Khalid Nouneh, A. Fahmi, M. Fahoume, A. Qachaou
Abstract
Lead-free tin halide perovskites, such as cubic-phase α -CsSnI 3 , face structural instability challenges in photovoltaic applications. Using density functional theory (DFT) with a 2 × 2 × 1 supercell, we investigate the effects of Zn and Cu doping on thermodynamic stability, elastic properties, and optoelectronic behavior. Cu doping enhances mechanical stability (bulk modulus: 18.1 GPa vs. 11.6 GPa for undoped) and improves dielectric response in the visible range. Zn doping narrows the bandgap to 0.45 eV and extends optical absorption into the near-infrared, though it introduces shear instability. Both dopants induce p-type conductivity, as indicated by Fermi-level shifts toward the valence band. Optical spectra reveal that Zn-doped CsSnI 3 exhibits strong near-infrared absorption ( α ( ω ) > 10 5 cm −1 ), while Cu doping enhances plasmonic peaks in the energy loss function at 2.3 eV. These findings highlight Cu-doped CsSnI 3 as a promising candidate for stable visible-light optoelectronics, while Zn-doped variants enable tunable absorption for low-energy photovoltaic applications. This study provides a detailed understanding of doping effects in lead-free perovskites, offering pathways for their performance optimization. • Cu doping stabilizes α -CsSnI3 and increases its bulk modulus to 18.1 GPa. • Zn reduces the bandgap to 0.45 eV, while Cu maintains a 1.40 eV indirect bandgap. • Both dopants induce p-type conductivity via Fermi-level shifts to the valence band. • Cu enhances plasmonic activity, while Zn enables strong near-infrared absorption. • Zn and Cu doping advance lead-free perovskites for photovoltaic applications.