Key Ionic Electrolytes for Highly Self‐Stable Light‐Emitting Electrochemical Cells Based on Ir(III) Complexes

Abstract Self‐stability in light‐emitting electrochemical cells (LECs) based on Ir(III) ionic transition metal complexes (Ir‐iTMC) has been long overlooked. Herein, it is demonstrated that the nature of the active layer blending an archetype Ir‐iTMC as emitter and ionic electrolytes—ionic liquid (IL) or ionic polyelectrolyte (IP)—is paramount for the storage and mechanical stability of rigid/flexible LECs. Strikingly, devices with ionic polyelectrolytes (IPs) stand out compared to those with traditional configurations with or without ILs. They exhibit i) superior brightness and efficiencies in rigid/flexible devices due to the higher photoluminescence quantum yield, ii) the best performance at pulsed current driving mode under inert/ambient operation conditions due to a slower growth of the doped regions, iii) enhanced device stabilities upon ambient/inert storage, resulting in <10% performance loss after 1 month of aging, and iv) the smallest performance loss (<10%) upon bending stress, since IPs prevent mechanically induced damage, preserving morphological and spectroscopic features. These findings are supported by steady‐state and time‐resolved emission spectroscopy, electrochemical impedance spectroscopy, microscopic and mechanical assays, along with the analysis of fresh and aged devices driven at different modes under inert/ambient conditions. Overall, this work highlights the need of revisiting new emitter:electrolyte combinations toward realizing highly self‐stable LECs.