Color-Tunable Organic Light-Emitting Diodes with Single Pt (O^N^C^N)-Dibenzofuran Emitter Exhibiting High External Quantum Efficiency of ≈30% and Superior Operational Lifetime.

Color-tunable organic light-emitting diodes (CT-OLEDs) have a large color-tuning range, high efficiency and operational stability at practical luminance, making them ideal for human-machine interactive terminals of wearable biomedical devices. However, the device operational lifetime of CT-OLEDs is currently far from reaching practical requirements. To address this problem, a tetradentate Pt(II) complex named tetra-Pt-dbf, which can emit efficiently in both monomer and aggregation states, is designed. This emitter has high T of 508 °C and large intermolecular bonding energy of -52.0 kcal mol⁻, which improve its thermal/chemical stability. This unique single-emitter CT-OLED essentially avoids the "color-aging issue" and achieves a large color-tuning span (red to yellowish green) and a high external quantum efficiency （EQE） of ≈30% at 1000 cd m as well as an EQE of above 25% at 10000 cd m. A superior LT operational lifetime of 520,536 h at a functional luminance of 100 cd m, which is over 20 times longer than the state-of-the-art CT-OLEDs, is estimated. To demonstrate the potential application of such OLEDs in wearable biomedical devices, a simple electromyography (EMG)-visualization system is fabricated using the CT-OLEDs.