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.