Suppression of Bimolecular Interactions via Bulky Blocking Groups in Tetradentate Pt(II) Complex for Efficient Organic Light-Emitting Diodes

Management of bimolecular interactions such as triplet-triplet annihilation (TTA) and triplet-polaron annihilation (TPA) is crucial to reduce exciton loss for achieving high efficiency. Among several strategies, one approach is to use bulky blocking groups to increase the intermolecular distance. In this work, we investigated the correlation between the volume of blocking groups and bimolecular interactions in Pt complexes. It was found that the bulkiness of substituents is pivotal for maximizing quantum efficiency in these devices. An exciton dynamics study conducted during device operation quantitatively analyzed the contribution of substituents to the operational mechanism of device, demonstrating that complexes with bulky 2,6-diisopropylphenyl and tert-butyl substituents enhance exciton harvesting by suppressing TTA and TPA, thereby facilitating Förster energy transfer from Pt complexes to fluorescent dopant.