Bright Orange Electroluminescence from Lead-Free Two-Dimensional Perovskites

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 (C18H35NH3)2SnBr4 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 [SnBr6]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.