Light-emitting electrochemical cells based on inorganic metal halide perovskite nanocrystals

All-inorganic perovskite nanocrystals (NCs), such as CsPbX₃ (X = Cl, Br, I) NCs, have become particularly interesting for lighting applications due to their efficient synthesis, higher stability over hybrid organic-inorganic perovskites (HOIP) and narrow emission bands associated with high photoluminescence quantum yields (PLQYs). However, a critical aspect is how to prepare pin-hole free films using solvent-based deposition techniques and additives to avoid electrochemically-induced degradation of the perovskites under device operation conditions. Here, we have synthesized all-inorganic CsPbX₃ NCs using a hot injection synthesis route and characterized their structural, morphological and photophysical properties in detail. Furthermore, we have integrated these NCs into light-emitting electrochemical cells (LECs), achieving a brightness of 8 cd m^-2 for the NCs comprising a mixture of bromide and iodide at low driving currents. Additionally, we have demonstrated that the use of the salt KCF₃SO₃ in the active layer not only decreases the injection voltage but also prevents halide segregation in perovskite NCs due to a further stabilization of the lattice with potassium ions. Overall, we believe that all-inorganic perovskite NCs are promising emitters for lighting devices, however, further efforts towards elucidating the interplay of the components of the active layer and driving schemes are necessary.