Ground state structure and optoelectronic properties of novel quasi-2D layered halide perovskites CsPb₂X₅ (X= Cl, Br, I) via first principle calculations

The ground state structure and optoelectronic properties of novel quasi-2D layered halide perovskites CsPb₂X₅ (X= Cl, Br, I) are investigated for the possible optoelectronic applications in light emitting, photodetectors, photoemission, and photovoltaic (PV) devices using first principle-based calculations of the density functional theory (DFT). In the structure composition of CsPb₂X₅, 2Pb²⁺ atoms coordinated with eight X^- anions build [Pb₂X₅]^- polyhedral layers, where two layers of [Pb₂X₅]^- polyhedron are separated by Cs⁺ (spacer cation) layers. The band gap nature of the studied semiconductors is indirect and spin orbit coupling (SOC) effect reduces the band gaps and splits the Pb-p and X-p orbitals at the edges of conduction and valence bands respectively. The wide and suitable band gaps of CsPb₂X₅ enable them for advanced technological applications in photodetectors, transistors, and optoelectronic devices. The dielectric functions, exciton binding energies, and carrier's effective masses show that CsPb₂X₅ are suitable materials for optoelectronic, photodetectors, and light emitting devices.