Spatially separated donor-acceptor design of host materials for independent control of photophysical properties and carrier transport properties

• Constant triplet energy in the bipolar host materials irrespective of an aromatic spacer.
• Design strategy of high triplet energy bipolar host material with improved thermal properties.
• High quantum efficiency and low driving voltage using bipolar type host materials.

Triplet host materials with spatially separated donor and acceptor moieties were synthesized and the effect of the spatial separation of the donor and acceptor moieties via aromatic linkage on the photophysical properties of the host materials was elucidated. It was revealed that the aromatic linkage had weak influence on the absorption and triplet energy of the donor-acceptor type host materials with completely separated donor and acceptor moieties. Charge transport properties and device performances were found to be changed by the type of the aromatic linkage. Therefore, the spatially separated donor-acceptor design was proven to independently control photophysical properties and charge transport properties.