Using an Organic Molecule with Low Triplet Energy as a Host in a Highly Efficient Blue Electrophosphorescent Device

Abstract

To achieve high efficiencies in blue phosphorescent organic light-emitting diodes (PhOLEDs), the triplet energies (T1) of host materials are generally supposed to be higher than the blue phosphors. A small organic molecule with low singlet energy (S1) of 2.80 eV and triplet energy of 2.71 eV can be used as the host material for the blue phosphor, [bis(4,6-difluorophenylpyridinato-N,C(2'))iridium(III)] tetrakis(1-pyrazolyl)borate (FIr6; T1=2.73 eV). In both the photo- and electro-excited processes, the energy transfer from the host material to FIr6 was found to be efficient. In a three organic-layer device, the maximum current efficiency of 37 cd A(-1) and power efficiency of 40 Lm W(-1) were achieved for the FIr6-based blue PhOLEDs.

Structure–property relationship of 4-substituted-spirobifluorenes as hosts for phosphorescent organic light emitting diodes: an overview

“…46,[54][55][56][57][58][59][60][61][62][63] Finally, another approach widely developed in literature consists to introduce a steric congestion within the dye in order to hinder the planarization between two connected π-systems, which in turn breaks the π-conjugation between them. [64][65][66] This 'steric hindrance' strategy is most of the time performed through the incorporation of a sterically hindered ortho linkage 65,67,68 efficiently leading to a π-conjugation restriction. This last strategy is the basis of ortho linked SBFs (substitution in position 4) [68][69][70][71] which will be developed in this review.…”

Benzimidazobenzothiazole‐Based Bipolar Hosts to Harvest Nearly All of the Excitons from Blue Delayed Fluorescence and Phosphorescent Organic Light‐Emitting Diodes

“…[7] Host materials are thus are important as emitters to determine overall device performance.A ni deal host should possess high triplet energy,a ppropriate frontier molecular orbital levels,b ipolar charge transport ability,and large spectral overlap with doped emitters. [8] To fulfill these requirements,m any donor and acceptor building blocks have been developed for host materials.…”

9H‐Quinolino[3,2,1‐k]phenothiazine: A New Electron‐Rich Fragment for Organic Electronics

“…[4] In addition to its high thermal/morphological stability and its high triplet energy (E T ), an ideal host should also possess a bipolar character with HOMO and LUMO energy levels adapted to the Fermi levels of the electrodes. [6][7][8][9] However, there is a certain antinomy between a high E T (essential to insure efficient energy transfers) and a short HOMO/LUMO gap (essential to insure efficient charge injection) and the best trade-off should be found for the ideal host. If the nature of the linkage [10] between the electron rich and the electron poor units is of key importance to control the E T as well as the HOMO/LUMO gap, their intrinsic properties remain nevertheless the most important characteristics.…”