One united atom force field has been designed specifically for OLED simulations, where the training set consisted of eight organic molecules commonly used as hosts in OLED research. This force field reproduced the experimental density of the eight molecules and that of two similar molecules outside the training set. Furthermore, it achieved a six-fold speed-up in condensed phase simulation compared to AMBER by treating hydrogen atoms implicitly. However, the lack of explicit hydrogen limits its usage in hydrogen-bonding systems and the study focused on ground state properties only.