Towards efficient terbium-based solution-processed OLEDs: Hole mobility increase by the ligand design

•The brightest solution-processed terbium-based OLED was obtained.•The approach towards emitter hole mobility increase by the ligand design was developed.•Recently studied material PO4 was used as a host able to both increase electron mobility and sensitize terbium luminescence.•The role of charge carrier mobility was directly demonstrated. The approach towards the increase of the terbium electroluminescence efficiency by the increase of the transport properties was further developed. Therefore, terbium-based emitters, containing anionic ligands, able to both increase the hole mobility and to sensitize terbium luminescence, were purposefully obtained within the composite films, containing the recently studied host material PO4, able to increase electron-transport properties and also to ensure terbium luminescence. As a result, the luminance of 332 cd/m2 was reached, which is one of the highest results for solution-processed OLEDs based on terbium complexes.