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 (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.

Metal halide perovskite nanocrystals and their applications in optoelectronic devices

“…), B site doping (with Mn 2+ , Ni 2+ , Sn 4+ , Ln 3+ , etc. ), surface engineering, matrix encapsulation, and postprocessing …”

“…For example, Zhang et al recently realized the preparation of lead‐free 2D (C 18 H 35 NH 3 ) 2 SnBr 4 perovskite NCs, and obtained PL QYs of 88% and 68% in colloidal suspension and in a film, respectively. Furthermore, the preparation of 350 cd/m 2 LEDs has been realized, which has significantly improved the application prospect of lead‐free perovskite NCs in environmentally friendly solid‐state lighting …”

“…), [257][258][259][260][261][262][263][264] surface engineering, 195,197 matrix encapsulation, 196,265 and postprocessing. 161,266,267 Coupled with lattice incompleteness, many defects are presented in these NCs, including Schottky defects (cation and anion vacancies), Frenkel defects (interstitial sites), inversion defects, and structural defects (grain boundary, interface, and lattice distortion caused by impurities). 268 The low defect formation energy of NCs allows ions to easily escape from the lattice and move along these defect sites.…”

“…Some researchers have prepared leadfree (replacing Pb with tin [Sn], bismuth [Bi], germanium [Ge], indium [In], and antimony [Sb]) perovskite NCs to reduce their toxicity, but they do not realize a high PL QY. 177,266,[278][279][280] For example, Zhang et al recently realized the preparation of lead-free 2D (C 18 H 35 NH 3 ) 2 SnBr 4 perovskite NCs, and obtained PL QYs of 88% and 68% in colloidal suspension and in a film, respectively. Furthermore, the preparation of 350 cd/m 2 LEDs has been realized, which has significantly improved the application prospect of lead-free perovskite NCs in environmentally friendly solid-state lighting.…”

“…Furthermore, the preparation of 350 cd/m 2 LEDs has been realized, which has significantly improved the application prospect of lead-free perovskite NCs in environmentally friendly solid-state lighting. 266 In addition, single crystal perovskites also exhibit high optical absorption, long carrier lifetime, large carrier mobility, low trap density, and high defect tolerance. Compared with polycrystalline films, single crystal perovskites can reduce the intragrain and intergrain defects that affect device performance and generally have good thermal stability and humidity stability compared with NCs.…”