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

Abstract 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 d of 508 °C and large intermolecular bonding energy of ‐52.0 kcal mol⁻ 1 , 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 −2 as well as an EQE of above 25% at 10000 cd m −2 . A superior LT 90 operational lifetime of 520,536 h at a functional luminance of 100 cd m −2 , 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.