The solid state solvation effect of a TADF emitter, PTZ-DBTO2, in hosts with different polarity has been previously studied in detail using a combined MD and TD-DFT approach. PTZ-DBTO2 consists of a phenothiazine donor (coloured in grey) and a dibenzothiophene-S,S-dioxide acceptor (coloured in black) as shown in Figure . Both X-ray data and DFT calculations show that the donor and acceptor arrangement can exist in two forms, referred to as axial and equatorial, with respect to the N-S axis and plane of the phenyl rings. The two forms are sometimes also referred as perpendicular and co-planar in the literature. The equatorial configuration is preferable for TADF due to the near perpendicular arrangement between the donor and the acceptor for this isomer. QM calculations reveal that the HOMO and LUMO orbitals reside mainly on the donor and the acceptor, respectively, with little overlap. The first singlet excitation of PTZ-DBTO2, which is dominated by the HOMO-LUMO transition, is known to possess a strong charge transfer character. The other two molecules shown in Figure , CBP and PYD2 are commonly used host materials in the OLED community. In this work, we model the excited state properties of PTZ-DBTO2 in these solid state hosts using the QUBE force field. We show that this molecule-specific force field notably allows us to model both geometric and environmental contributions to the Stoke's shift of PTZ-DBTO2, which was missing from previous studies which used transferable MM force fields. 2 Computational Methods