Improving the Stability and Efficiency of Blue Organic Light-Emitting Diodes via Remote <i>tert</i> -Butyl Modification on a Pt(II) complex

High-quality phosphors are pivotal in achieving high-performance deep-blue organic light-emitting diodes (OLEDs) confronting the critical challenge of high efficiency and long lifespan. Here, we report a new Pt(II) emitter, PtON-H, by introducing a <i>tert</i>-butyl (<i>t-</i>Bu) moiety on the carbene site of the ligand based on the imminent emitter PtON-TBBI. The <i>t</i>-Bu group in PtON-H minimally affects the central conformation but increases the molecular volume by 10% and enhances vibration decoupling for the phosphorescent emission compared to PtON-TBBI. Thus, PtON-H has almost the same emission spectrum as PtON-TBBI but demonstrates higher photoluminescence quantum yield and radiative decay rate in both dichloromethane solution and a solid host. The corresponding phosphorescent OLED incorporating PtON-H achieved a 10.4% higher external quantum efficiency (EQE) of 17% and a 2-fold life-span improvement of LT₉₀ = 69 h at 1000 cd/m² over the PhOLED device based on PtON-TBBI. The corresponding deep-blue phosphor-sensitized OLED using PtON-H realized a high maximum EQE of 18.9%, an LT₉₀ of 37 h, and a CIE coordinate of (0.14, 0.15). These findings provide insights into a dynamically driven strategy for improving the electroluminescent performance of phosphors.