Theoretical design study on multifunctional triphenyl amino‐based derivatives for OLEDs

The use of triphenyl amino‐based derivatives in organic light‐emitting diodes (OLEDs) can significantly improve their efficiency and stability and especially their electroluminescence characteristics – most of the new hole‐transport materials have this feature. In this study, a series of triphenyl amino‐based compounds were computed, including two newly designed molecules. They can function as charge transport materials and emitters with high efficiency and stability. To reveal the relationship between the properties and structures of these bifunctional and multifunctional electroluminescent materials, the ground and excited state geometries were optimized at the B3LYP/6‐31G(d), HF/6‐31G(d), TD‐B3LYP/6‐31G(d), and CIS/6‐31G(d) levels, respectively. The ionization potentials (IPs) and electron affinities (EAs) were computed. The lowest excitation energies, the maximum absorption, and emission wavelengths of these compounds were calculated by employing the time‐dependent density functional theory (TD‐DFT) method. Also, the mobilities of holes and electrons were studied computationally based on the Marcus electron transfer theory. The CH₂Cl₂ solvent effect on the absorption spectra of N,N′‐di‐1‐naphthyl‐N,N′‐diphenylbenzidine ( NPB ) was considered by polarizable continuum model (PCM). The results obtained for these compounds are in good agreement with the experimental values. These data show that the proposed compounds 1 and 2 (N,B‐di‐1‐naphthyl‐N,B‐diphenylbenzidine and Mes₂Np‐4,4′‐biphenyl‐NPh(1‐naphthyl)]), are multifunctional and bifunctional materials similar to Mes₂Bp‐4,4′‐biphenyl‐NPh(1‐naphthyl)] ( BNPB ) and NPB , respectively. Copyright © 2009 John Wiley & Sons, Ltd.