High-efficiency optoelectronics via quantum confinement in Ruddlesden–Popper pseudo-halide perovskites

Layered halide perovskites are strong candidates for applications, including solar cells, light-emitting diodes and photodetectors, because of their diverse photo-physical properties. In this study, we use first-principles density functional theory (DFT) to investigate an all-inorganic two-dimensional pseudohalide perovskite, Cs 2 Pb(SeCN) 2 Br 2 . Its three-dimensional crystal structure consists of two-dimensional perovskite layers that act as quantum wells for electrons and holes, while one-dimensional spacer slabs create energy barriers that confine the carriers. The incorporation of pseudo ion not only reduces the quantum confinement but also the binding energy, which enhances the optoelectronic response. Electronic-structure calculations reveal a direct band gap of 2.57[Formula: see text]eV, a low binding energy of 145[Formula: see text]meV and a small interlayer distance of only 1.74[Formula: see text]Å. From optical simulations, the material exhibits tunable bandgap, visible-range absorption and photoluminescence, features that favor its use in optoelectronic devices and solar cells. To compute the compound’s photovoltaic (PV) potential, we model a complete cell with the stack fluorine-doped tin oxide, tin oxide, Cs 2 Pb(SeCN) 2 Br 2 , copper(I) oxide and gold, optimizing power conversion through variation of the absorber thickness. In the new solar-cell architecture, SnO 2 functions as the electron transport layer (ETL) and Cu 2 O serves as the hole transport layer (HTL). Under optimum conditions, the device records a fill factor (FF) of 80.1%, an open-circuit voltage of ([Formula: see text]) 1.89[Formula: see text]V, a power-conversion efficiency (PCE) of 25.60% and a short-circuit current density of ([Formula: see text]) 16.5[Formula: see text]mA[Formula: see text]cm[Formula: see text]. These findings provide a new way for studies of all-inorganic pseudohalide perovskite absorbers and point toward further improvements in solar-cell performance through both experimental work and theoretical modeling.