Computational insight into lead-free quasi-1D layered halide perovskites Cs₂AgX₃ (<i>X</i> = Cl/Br/I) for optoelectronic applications

The structure configuration, thermodynamic stability and optoelectronic characteristics of lead-free quasi-1D layered halide perovskites (LHPs) Cs 2 AgX 3 ([Formula: see text] Cl/Br/I) have been explored using first-principles density functional theory (DFT) calculations. These investigations aim to evaluate their potential for optoelectronic applications such as light-emitting and photovoltaic (PV) devices. The structure composition of Cs 2 AgX 3 ([Formula: see text] Cl/Br/I) is crystallized in orthorhombic symmetry with the Pnma space group. Their structure is composed of isolated AgX 4 tetrahedra separated by Cs ions, forming a quasi-1D configuration that induces strong quantum confinement effects. The thermodynamic stability of these materials is validated by their positive change in entropy ([Formula: see text], which leads to a negative change in Gibbs free energy ([Formula: see text]. Additionally, the specific heat capacity curves align with the Dulong–Petit law and adhere to the equipartition theorem of classical mechanics. These quasi-1D-LHPs exhibit a direct band gap nature, and their band gaps reduce with the SOC effect that causes splitting of the halide and Ag p-orbitals at the edges CB and VB, respectively. The direct band gap nature makes Cs 2 AgX 3 highly efficient for optoelectronic applications in transistors, PV and light-emitting devices. The effective mass of charge carriers, carrier’s mobility and optical coefficients (dielectric functions) make these quasi-1D-Cs 2 AgX 3 ([Formula: see text] Cl/Br/I) well-suited for aforementioned applications within the visible to UV energy range of the electromagnetic spectrum.