Sn/Ge Substitution in ((C_nH_2n–1NH₃)₂PbI₄; n = 3–6): An Emerging 2D Layered Hybrid Perovskites with Enhanced Optoelectronic Properties

Abstract

Two-dimensional (2D) perovskites show higher stability in comparison to their three-dimensional (3D) counterparts. Therefore, 2D perovskites have invoked remarkable attention in the basic understanding of their physical properties and optoelectronic applications. Here, we present a lowdimensional naturally self-assembled inorganic−organic (IO) hybrid system based on a primary cyclic ammonium-based (C n H 2n−1 NH 3 ) semiconductor series [viz. ((C n H 2n−1 NH 3 ) 2 PbI 4 , n = 3−6)]. However, the wide bandgap nature and presence of toxicity because of lead (Pb) prohibit their applications. Therefore, in the present work, we study the role of Ge/Sn substitution and Pb vacancy (Pb-□) to reduce the concentration of Pb and to enhance the solar cell efficiency by the formation of mixed perovskite structures. We have discussed the effect of spin− orbit coupling (SOC) using state-of-the-art hybrid density functional theory (DFT). We find the mixed conformers with Pb-□ do not possess structural stability. Moreover, they have an indirect bandgap, which is not good for solar cell applications. Only those conformers that have favorable thermodynamics and structural stability are considered for further study of optical properties. Our results infer that Sn substitution is more favorable than that of Ge in replacing Pb and enhancing the efficiency. Exciton binding energies calculated using the Wannier−Mott approach for pristine and substituted conformers are larger than lead halide perovskites, whereas the electron− phonon coupling is smaller in the former. From computed spectroscopic limited maximum efficiency (SLME), these 2D perovskites show enough promise as alternatives to conventional lead halide perovskites.

Forecasting the unrevealed surface-controlled photocatalytic water splitting in two-dimensional Ag2Se with ultrafast carrier mobility: a first-principles study

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