Strong Thickness-Dependent Quantum Confinement in All-inorganic Perovskite Cs2PbI4 with Ruddlesden-Popper Structure
In recent years, two-dimensional (2D) organic-inorganic perovskites have been attracted considerably attention as the unique performance and enhanced stability for the photovoltaic solar cells or photoluminescent device. However, how the two-dimensionality affects the photoelectric properties of all-inorganic perovskites remains unclear. In this work, the electronic and optical properties including band structures, carrier mobility, optical absorption spectra and exciton-binding energies for the all-inorganic perovskite Cs2PbI4 with Ruddlesden-Popper (RP) structure are investigated systemically by using density functional theory with spin orbit coupling (SOC) effect. The calculated results demonstrate the thickness-dependent of electronic properties in the all-inorganic 2D RP perovskite Cs2PbI4 and their carrier mobility which is comparable to that of CsPbI3 thin films. The exciton-binding energies of perovskite Cs2PbI4 with RP structure increase with the decrease of number of layers. Besides, the value of exciton-binding energiey for monolayer (181.70 meV) more than 3 times larger than that of CsPbI3 (59.12 meV). Moreover, the calculated results show that two dimensional layered Ruddlesden-Popper perovskite Cs2PbI4 may be not a good material for photovoltaic applications due to their low carrier mobility and poor visible light absorption, but may be a good material for light-emission applications due to their larger thickness-dependent exciton binding energy. Our work would provide a theoretical basis for other ultrathin two-dimensional Perovskite materials with potential application for photoluminescent device or solar absorbers.