Carbazole‐endcapped Spiro[fluorene‐9,9′‐xanthene] with Large Steric Hindrance as Hole‐transporting Host for Heavily‐doped and High Performance OLEDs

In this work, we designed and synthesized a novel spirocyclic compound functionalized spiro[fluorene‐9,9′‐xanthene] with carbazole group (2‐carbazolyl‐spiro[fluorene‐9,9′‐xanthene], SFX‐Cz ) via Friedel‐Crafts and Ullmann reaction, which is expected to own high thermal and morphological stability, and good carrier injection/transporting properties due to the excellent hole transporting characteristics of carbazole and cruciform structure of spiro[fluorene‐9,9′‐xanthene]. The carbazole end‐capped spiro[fluorene‐9,9′‐xanthene] SFX‐Cz based PhOLEDs with FIrpic as phosphor emitter have been researched by varying dopant concentration, which exhibit the maximum EQEs of 8.9%, 7.4%, 9.1%, and 4.7% with the doping increasing from 10% to 50%. The higher performance PhOLEDs are independent on concentration variation from 10% to 30%, which suggests the bulky steric hindrance of SFX‐Cz might be a potential canditate for high performance and inexpensive device with simplified process.