Synthesis and characterization of spiro(adamantane-2,9 '-fluorene)-based triaryldiamines: thermally stable hole-transporting materials

Abstract

New triaryldiamines. Adm-TPD and Adm-NPD, which contain a spiro(adamantane-2,9-fluorene) core, have been synthesized and characterized. We believe that because of the presence of the rigid spiro-fluorene core, these triaryldiamines exhibit higher glass transition temperatures and have a less tendency to crystallize relative to their biphenyl analogs. Additionally, electrochemical studies showed that the planarity of the fluorene core leads to lower ionization potentials and greater degrees of pi conjugation between the two amino groups. AFM measurements demonstrated that high-quality amorphous films of Adm-NPD with good morphological stability were prepared by vapor deposition. Electroluminescent devices using Adm-NPD as a hole-transporting layer-i.e., having the configuration ITO/Adm-NPD/Alq(3)/LiF/Al-emit a bright green light that is characteristic of Alq(3). (C) 2003 Elsevier B.V. All rights reserved.