Molecular hosts for triplet emission in light emitting diodes: A quantum-chemical study

Correlated semiempirical and ab initio quantum-chemical methods are applied to the description of the lowest-lying triplet excited state, T1, in conjugated molecules used as hosts in phosphorescent light emitting diodes. Density functional theory is found to lead to the best agreement between measured and calculated excitation energies in a set of reference molecules. The trade-off between the barrier for charge injection and the singlet–triplet S0 → T1 energy spacing is discussed in the context of the design of molecular hosts for blue triplet guest emitters.