Disentangling Energy Transfer Pathways in Donor–Acceptor Dyads: A Molecular-Level Perspective for TADF OLED Applications

A comprehensive understanding of the nonradiative energy transfer process is critical for advancing emitter design in organic light-emitting diodes (OLEDs). This study employs a multiscale computational approach integrating classical molecular dynamics, quantum chemical calculations, and kinetic Monte Carlo simulations to investigate a multiresonant (MR) emitter dyad (Cy-tmCPBN) in pure and doped film morphologies. Our results show that film morphology and molecular orientation critically influence energy transfer efficiency. In the pure film, tight molecular packing and favorable donor–acceptor alignment promote efficient intermolecular energy transfer. In contrast, doping with a donor host (Cy-tmCP)─which incorporates the same donor fragment as Cy-tmCPBN─introduces spatial dilution and disrupts molecular alignment, yielding reduced resonance energy transfer rates. Quantum mechanical analyses based on interfragment charge transfer and noncovalent interaction frameworks reveal that while the excitations are predominantly localized, weak yet non-negligible intermolecular electronic coupling in the pure film facilitates the observed energy transfer. These findings underscore the importance of tuning molecular organization and structural rigidity to control exciton behavior and optimize energy transfer in OLED emitter layers, aligning with ongoing efforts to improve device performance through rational molecular design.