High triplet energy electron transport side-chain polystyrenes containing dimesitylboron and tetraphenylsilane for solution processed OLEDs

A series of polystyrenes was developed as electron transport materials (ETMs) for solution processed organic light emitting diodes (OLEDs), containing dimesitylboryl (BMes2) and tetraphenylsilanyl in their side-chains. The synthesis and characterisation of the polymers is reported. High triplet energy up to 2.95 eV was obtained for ETMs containing BMes2 and tetraphenylsilanyl. High glass transition temperatures over 180 °C were detected for the series due to the polymer approach, ensuring high thermal stability. The role of both molecular motifs was evaluated in Ir based green OLEDs with all organic layers processed from solution. Similar current efficacies around 30 cd A-1 were measured for the electron-transport polymers, most likely due to the confinement of the LUMO delocalization into the BMes2 unit, leading to similar charge mobility. These results show that incorporation of BMes2 into polymers is an adequate approach for further development of wet-process materials.