Stable, High‐Efficiency Voltage‐Dependent Color‐Tunable Organic Light‐Emitting Diodes with a Single Tetradentate Platinum(II) Emitter Having Long Operational Lifetime

Voltage-dependent, color-tunable organic light-emitting diodes (OLEDs) are appealing tools that can be used for the visualization of electronic output signal of sensors. Nonetheless, the literature-reported color-tunable OLEDs that have a simple single-cell device structure suffer from relatively low efficiency, pronounced efficiency roll-off, color-aging, and short operation lifetime, all of which limit their practical applications. Here, a novel co-host-in-double-emissive-layer (CHIDEL) device, designed to enhance the performance of color-tunable OLEDs with the use of a single tetradentate PtO^ N^ C^ N emitter, is described. When Pt-X-2 is used as a single emitter in an optimized CHIDEL device, a white OLED with tunable Commission International de I'Eclairage (CIE) coordinates from (0. 47, 0. 44) at 3 V to (0. 36, 0. 48) at 11 V, a high color rendering index of 82, and high external quantum efficiency (EQE) of up to 20. 75% can be achieved. By using Pt-X-4 as a single emitter, the voltage-dependent color-tunable CHIDEL device, with CIE coordinates shifted from (0. 56, 0. 43) at 3 V to (0. 42, 0. 55) at 11 V, demonstrates a high luminance of beyond 90 000 cd m-2 and a high EQE of 23. 23% at a luminance of 1300 cd m-2. A long-lifetime time to 90% of the initial luminance (LT90) of almost 20 000 h is demonstrated for the color-tunable OLED with Pt-X-4 emitting dopant.