Development of Next-Generation OPLS Force Field for Accurate Modeling of Phosphorescent OLED Materials

<b>To address the inherent challenges of modeling organometallic complexes, which are commonly used as phosphorescent emitters in OLEDs, the OPLS4 force field is extended in order to have a more suitable functional form. These new developments include a fluctuating charge model to describe charge transfer, a Morse potential to describe the metal-ligand bonding, and an angular overlap model to describe d-orbital effects. The initial force field coverage is centered around common chemistries found in Pt(II) and Ir(III)-based emitters. Our model accurately represents geometries when comparing against DFT and crystal structure references. In addition, the model was validated on a series of organometallic emitters doped into an organic host layer, generating configurations from molecular dynamics simulations that are used to predict photoelectronic properties. Future developments include the extension of chemical coverage in the effort to more broadly aid in material design.</b>