48‐4: Toward the Achieving Excellent Longevity of Blue OLED Device: A Computation Study on Importance of the Co‐optimization of Material and Device

The device lifetime of phosphor mediated TADF OLED, which is composed of three different type of materials such as host, phosphorescence, and TADF emitters in EML, was systematically investigated by a multi‐scale approach from quantum mechanics simulation to kinetic Monte Carlo simulation. The quantum chemical simulations to estimate the chemical stability of materials in atomic scale were clearly showed that the photo‐ or electro‐chemical stability in excited state was good qualitative correlation with device lifetime. From the results, we could figure out the crucial parameters that strongly related with the lifetime of blue TADF devices. Then, the device simulations based on kinetic Monte Carlo method were performed to understand excitonic dynamic. Based on the understanding about both a role of phosphorescence and a mechanism of energy transfer through emitters in EML, we found out that a concentration of triplet exciton around TADF emitters could be a dominant origin of the short lifetime even if TADF would have a sufficient stability condition we expect, and should be reduce to prevent the excitonic stress such as triplet‐triplet annihilation and triplet‐polaron quenching, resulting in the degradation of emitters. Consequently, this work suggests the simultaneous co‐optimization of both the device and its component material, for deep blue OLED device with a longer lifetime.