Selection of contact materials to p-type halide perovskite by electronegativity matching

The performance of perovskite optoelectronic devices depends critically on the contact between the active layer and charge transport materials. To reveal the mechanism of barrier formation on perovskite surfaces, we studied Schottky junctions between various metals and a p-type perovskite CsSnBr3. By constructing slab models of the junction interface and aligning atomic core levels, the contacts between Au/CsSnBr3 and graphite/CsSnBr3 were found to be ohmic, but various other metals produced Schottky junctions with CsSnBr3. These calculation results, supported by x-ray photoelectron spectroscopy measurements, suggest that the barrier height of a metal/CsSnBr3 junction is a linear function of the metal’s electronegativity, rather than its work function. By introducing the concept of effective electronegativity for compounds, this trend was extended to a general rule that a suitable transport material should have an effective electronegativity to match that of the perovskite.