Polymer\nHosts Containing Carbazole-Dibenzothiophene-Based\nPendants for Application in High-Performance Solution-Processed TADF-OLEDs

The\nfilm-forming capability of the host plays a crucial role in\neffectively forming a light-emitting layer through a solution process\nin organic light-emitting diodes (OLEDs). In this study, we synthesized\ntwo side-chain polymer hosts, <b>PCz-DBT</b> and <b>P2Cz-DBT</b>, consisting of carbazole and dibenzothiophene. The synthesis was\ncarried out through radical polymerization using styrene-based host\nmonomers. Their photophysical characteristics and molecular energy\nlevels are similar to those of the reference small molecule hosts,\nnamely, Cz-DBT and 2Cz-DBT. However, compared to the small-molecule\nhosts Cz-DBT and 2Cz-DBT, the two polymer hosts showed high thermal\nstability and good film-forming properties in the neat and host–emitter\nblend films. Specifically, bluish-green multiple-resonance (MR) thermally\nactivated delayed fluorescence (TADF) OLEDs, fabricated via solution\nprocessing with an emissive layer based on <b>P2Cz-DBT</b>,\nexhibited remarkable performance. These devices achieved a maximum\nexternal quantum efficiency of 17.4% without utilizing a hole transport\nlayer. This polymer host design strategy is considered to significantly\ncontribute to enhancing the performance of TADF-OLEDs fabricated through\nsolution processing.