Simple, fast, bright, and stable light sources.

In this work we show that solution-processed light-emitting electrochemical cells (LECs) based on only an ionic iridium complex and a small amount of ionic liquid exhibit exceptionally good performances when applying a pulsed current: sub-second turn-on times and almost constant high luminances (>600 cd m(-2) ) and power efficiencies over the first 600 h. This demonstrates the potential of LECs for applications in solid-state signage and lighting.