Light-emitting diodes based on all-inorganic copper halide perovskite with self-trapped excitons

Light-emitting diodes based on lead halide perovskite have attracted great attention due to their outstanding performance. However, their application is plagued by the toxicity of Pb and the poor stability. Herein novel copper-based all inorganic perovskite CsCu₂I₃ with much enhanced stability has been reported with a potential photoluminescence quantum yield (PLQY) over 20% and self-trapped excitons (STE). By taking advantage of its extraordinary thermal stability, we successfully fabricate high-quality CsCu₂I₃ film through direct vacuum-based deposition (VBD) of CsCu₂I₃ powder. The resulting film shows almost the same PLQY with the synthesized powder, as well as excellent uniformity and stability. The perovskite light-emitting diodes (Pe-LED) based on the evaporated CsCu₂I₃ emitting layer achieve a luminescence of 10 cd/m² and an external quantum efficiency (EQE) of 0.02%. To the best of our knowledge, this is the first CsCu₂I₃ Pe-LED fabricated by VBD with STE property, which offers a new avenue for lead-free Pe-LED. (paper)