title: Steric engineering of metal-halide perovskites with tunable optical band gaps.
abstract: Owing to their high energy-conversion efficiency and inexpensive fabrication routes, solar cells based on metal-organic halide perovskites have rapidly gained prominence as a disruptive technology. An attractive feature of perovskite absorbers is the possibility of tailoring their properties by changing the elemental composition through the chemical precursors. In this context, rational in silico design represents a powerful tool for mapping the vast materials landscape and accelerating discovery. Here we show that the optical band gap of metal-halide perovskites, a key design parameter for solar cells, strongly correlates with a simple structural feature, the largest metal-halide-metal bond angle. Using this descriptor we suggest continuous tunability of the optical gap from the mid-infrared to the visible. Precise band gap engineering is achieved by controlling the bond angles through the steric size of the molecular cation. On the basis of these design principles we predict novel low-gap perovskites for optimum photovoltaic efficiency, and we demonstrate the concept of band gap modulation by synthesising and characterising novel mixed-cation perovskites.
authors.affiliation: Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
authors.forename: Marina R
authors.initials: MR
authors.lastname: Filip
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Giles E
authors.initials: GE
authors.lastname: Eperon
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith
authors.affiliation: Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
authors.forename: Feliciano
authors.initials: F
authors.lastname: Giustino