Enhanced Luminance of Electrochemical Cells with a Rationally Designed Ionic Iridium Complex and an Ionic Additive.

Light-emitting electrochemical cells (LEECs) offer the potential for high efficiency operation from an inexpensive device. However, long turn-on times and low luminance under steady-state operation are longstanding LEEC issues. Here, we present a single-layer LEEC with a custom-designed iridium(III) complex and a lithium salt additive for enhanced device performance. These devices display reduced response times, modest lifetimes, and peak luminances as high as 5500 cd/m2, 80% higher than a comparable device from an unoptimized complex and 50% higher than the salt-free device. Improved device efficiency suggests that salt addition balances space charge effects at the interfaces. Extrapolation suggests favorable half-lives of 120 ± 10 h at 1000 cd/m2 and 3800 ± 400 h at 100 cd/m2. Overall, complex design and device engineering produce competitive LEECs from simple, single-layer architectures.