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.