Bipolar tetraphenylsilane-based host molecules for blue phosphorescence

A class of bipolar host molecules with the linkage of hole-transporting groups (diphenylamine and N-phenylcarbazole) and electron-transporting units (pyridine and carboline) to tetraphenylsilane (TPSi) core were designed for blue phosphorescence by means of quantum-chemical calculations. The geometrical and electronic structures, triplet energies, and charge injection and transport properties of the designed host molecules were analyzed in details. The calculated results indicate that the designed molecules possess the triplet energies larger than 2.80 eV and might be the potential host materials for blue phosphorescence. The positions of N atom in pyridine and carboline have significant effects on molecular geometry, dipole moment, LUMO level, triplet energy, and electron reorganization energy. This work provides an in-depth understanding of the structure-property relationship of the TPSi-based host molecules, and offers the guideline for the screening of the efficient bipolar host materials for blue phosphorescence.