Non-toxic KGeX3 (X= I, Br, Cl) monolayer perovskites as an absorption layer in solar energy converters: A first principle study

Abstract

The study of Ge-based perovskite materials aims to reduce pollution and create highly efficient perovskite-based solar cells. We investigate the structural, electronic, and optical properties of bulk and monolayer forms of KGeX₃ (where X = I, Br, or Cl) perovskites using density functional theory (DFT). Phonon dispersion curves confirm the dynamic stability of KGeX₃. Several materials in the field exhibit direct bandgap semiconductor properties. As we progress from I to Br and from Br to Cl in KGeX₃, there is a clear trend of increasing bandgap values. The static dielectric constant of KGeI₃ is higher than that of KGeBr₃ and KGeCl₃, indicating a lower carrier recombination rate. A redshift is also observed in the absorption coefficient data as the transition in KGeX₃ progresses from Cl → Br → I. The efficiencies of bulk KGeI₃, KGeBr₃, and KGeCl₃ were estimated to be approximately 15.57 %, 23.43 %, and 31.70 %, respectively, using the Shockley-Queisser (SQ) limit. For monolayer forms, the efficiencies of KGeI₃, KGeBr₃, and KGeCl₃ were found to be approximately 28.77 %, 32.38 %, and 22.99 %, respectively. The KGeX₃ nanoparticle structure is promising for the light-absorbing layer in solar photovoltaic applications.