Jian He - Nonconjugated Carbazoles: A Series of Novel Host Materials for Highly Efficient Blue Electrophosphorescent OLEDs

Version 1

      Publication Details (including relevant citation   information):

      J. Phys. Chem. C, 113, 6761–6767 (2009)

    DOI: 10.1021/jp808801q

    Publication Date (Web): March 30, 2009

      Abstract:

      A series of carbazole derivatives was synthesized and their   electrical and photophysical properties were investigated. It is   shown that the triplet energy levels of these hosts are higher   than that of the most popular blue phosphorescent material   iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2′]   picolinate (FIrpic) and the most extensively used phosphorescent   host material 4,4′-N,N′-dicarbazole-biphenyl   (CBP). These new host materials also showed good thermal   stability and high glass transition temperatures   (Tg) ranging from 78 to 115 °C as the linkage   group between the carbazoles was altered. Photophysical   measurements indicate that the energy transfer between these new   hosts and FIrpic is more efficient than that between CBP and   FIrpic. Devices incorporating these novel carbazole derivatives   as the host material doped with FIrpic were fabricated with the   configurations of ITO/NPB (40 nm)/host:FIrpic (30 nm)/BCP (15   nm)/AlQ (30 nm)/LiF (1 nm)/Al (150 nm). High efficiencies (up to   13.4 cd/A) have been obtained when 1,4-bis   (4-(9H-carbazol-9-yl)phenyl)cyclohexane (CBPCH) and   bis(4-(9H-carbazol-9-yl)phenyl) ether (CBPE) were used   as the host, respectively. Efficiencies obtained from these   devices are significantly higher than the efficiency obtained   with CBP as the host. At a bias voltage of 20   V the maximum luminances of 20342   and 17766   cd/m2 were achieved for CBPCH- and CBPE-based devices,   respectively, which demonstrates that CBPCH and CBPE can be   excellent host materials for blue electrophosphorescent OLEDs.

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/jp808801q?journalCode=jpccck&quickLinkVolume =113&quickLinkPage=6761&volume=113