Bright Orange Electroluminescence from Lead-Free Two-Dimensional Perovskites

Abstract

Lead halide perovskites are important materials for solar cells and light emitting diodes (LEDs), but the toxicity of lead is a matter of concern for these and other commercial applications. Here, we demonstrate a lead-free two-dimensional (2D) Ruddlesden-Popper-type (C<inf>18</inf>H<inf>35</inf>NH<inf>3</inf>)<inf>2</inf>SnBr<inf>4</inf> perovskite with a strong emission from the self-trapped states, whose photoluminescence quantum yields in colloidal suspension and in a film are 88 and 68%, respectively. The insulating character of the organic oleylamine cation prevents electronic band formation between the [SnBr<inf>6</inf>]^4- octahedron layers, which results in the Stokes-shifted orange emission. Electroluminescence of these 2D lead-free perovskite materials was demonstrated in an inverted LED structure with a low turn-on voltage of 2.2 V and a luminance of 350 cd/m².