A Highly Efficient Universal Bipolar Host for Blue, Green, and Red Phosphorescent OLEDs

Investigation of the High Electron Affinity Molecular Dopant F6‐TCNNQ for Hole‐Transport Materials

“…[5] However, its efficiency drops considerably in host materials with IE larger than 5.40 eV. [5][6][7] Since large band gap hole transport materials (HTM) with higher IE are ubiquitous in many organic devices, [8,9] strongly oxidizing molecular dopants with larger EA, such as F6-TCNNQ films prepared on different substrates by thermal deposition as well as spin coating, to measure F6-TCNNQ films with different morphologies [Section S1, Supporting Information]. The LUMO and unoccupied states of the films are shown in Figure 2a.…”

Theoretical investigation of the degradation mechanisms in host and guest molecules used in OLED active layers

“…More importantly, its triplet energy E T (2.55 eV) 40 is too low for sky-blue phosphors such as FIrpic. 41 Phosphine oxide (PO) 15,16,[42][43][44][45][46][47][48][49] and sulfone (SO 2 ) 50, 51 derivatives with high triplet energy have emerged as host materials for blue electrophosphorescence and have also been successfully utilized in OLEDs. For example, 4,4'-bis(diphenylphosphine oxide) biphenyl (PO1), synthesized by Sapochak and co-workers, 49 has a triplet exciton energy (2.72 eV) higher than CBP through substitution of the carbazoles with diphenylphosphoryl (Ph 2 P=O) groups; the reason is that the P=O group prevents electronic communication between the central diphenyl core and the outer phenyl groups.…”

“…Depending on the nature of the cyclometalating and ancillary ligands, the relative energies of these states can vary considerably, resulting in different stabilities and device lifetimes. As the phosphorescent materials are distributed within an appropriate organic semi-conductive host matrix to avoid selfquenching of phosphors, [13][14][15] stability of the matrix molecules is also required. Previous attempts at understanding the lifetime of the host materials have focused on requiring a high-glass transition temperature (T g ), electrochemical stability, and morphological stability.…”

“…Previous attempts at understanding the lifetime of the host materials have focused on requiring a high-glass transition temperature (T g ), electrochemical stability, and morphological stability. 15,16 The triplet energy (E T ) of the host molecules must be higher than that of the emitter (dopant) to suppress energy back transfer. 17 Thus, degradation problems are particularly acute in blue OLEDs as the energies involved in the molecular excitation processes are in the same range as the homolytic cleavage of single bonds between second and third-row atoms, on the order of 2-3 eV.…”

Efficient non-doped blue organic light-emitting diodes: donor–acceptor type host materials

“…Though blue phosphorescent devices with high external quantum efficiencies have been reported, due to short device lifetimes they are not yet commercially used. [10][11][12][13] Therefore, to commercialise efficient blue OLEDs there is an urgent need to develop blue emissive materials.…”