oCBP is an organic semiconducting host material for highly efficient phosphorescent OLED and TADF devices, featuring a biphenyl linker and two electron-rich carbazole units, and a sterically hindered isomer of the well-known OLED host materials CBP and mCBP. The bulky carbazolyl groups at the 2 and 2' (ortho) positions of the biphenyl backbone creates significant steric repulsion. To minimize this repulsion, the two phenyl rings of the biphenyl unit are forced into a non-planar, highly twisted orientation. This steric hindrance and non-planar configuration also disrupt conjugation to gain a higher triplet energy state suitable for hosting deep-blue emission.
Known for its high triplet energy, good thermal, and morphological stability that ensures efficient energy transfer to the phosphorescent emitter (dopant) and effectively confines excitons within the emissive layer of the device. Being electron donating, oCBP frequently forms exciplexes when mixed with triazine-based or pyridine-based n-type hosts like mSiTrz or CNCzPyDFCN. PhOLED based on CN–Ir as the blue phosphorescent emitter and oCBP:CNCzPyDFCN as the mixed exciplex host demonstrates a high external quantum efficiency (EQE) of over 29% and a device lifetime of LT50 = 33.9 h at an initial luminescence of 1000 cd m−2 with a low turn-on voltage.
Also, due to its high triplet energy and large energy gap, oCBP acts as exciton blocking later (EBL) to make it difficult for high-energy blue excitons to transfer, effectively confining them within the EML where they can recombine radiatively to produce light.
* Sublimation is a technique used to obtain ultra pure-grade chemicals, see sublimed materials for more sublimed materials.