Lead-Free Antimony-Based Light-Emitting Diodes through the Vapor-Anion-Exchange Method

Hybrid lead halide perovskites continue to attract interest for use in optoelectronic devices such as solar cells and light-emitting diodes. Although challenging, the replacement of toxic lead in these systems is an active field of research. Recently, the use of trivalent metal cations (Bi³⁺ and Sb³⁺) that form defect perovskites A₃B₂X₉ has received great attention for the development of solar cells, but their light-emissive properties have not previously been studied. Herein, an all-inorganic antimony-based two-dimensional perovskite, Cs₃Sb₂I₉, was synthesized using the solution process. Vapor-anion-exchange method was employed to change the structural composition from Cs₃Sb₂I₉ to Cs₃Sb₂Br₉ or Cs₃Sb₂Cl₉ by treating CsI/SbI₃ spin-coated films with SbBr₃ or SbCl₃, respectively. This novel method facilitates the fabrication of Cs₃Sb₂Br₉ or Cs₃Sb₂Cl₉ through solution processing without the need of using poorly soluble precursors (e.g., CsCl and CsBr). We go on to demonstrate electroluminescence from a device employing Cs₃Sb₂I₉ emitter sandwiched between ITO/PEDOT:PSS and TPBi/LiF/Al as the hole and electron injection electrodes, respectively. A visible-infrared radiance of 0.012 W·Sr^-1·m^-2 was measured at 6 V when Cs₃Sb₂I₉ was the active emitter layer. These proof-of-principle devices suggest a viable path toward low-dimensional, lead-free A₃B₂X₉ perovskite optoelectronics.