A Series of Dibenzofuran‐Based n‐Type Exciplex Host Partners Realizing High‐Efficiency and Stable Deep‐Red Phosphorescent OLEDs

Abstract

Deep‐red to near‐infrared (NIR) OLEDs, which yield emission peak wavelengths beyond λ=660 nm, are applicable as unique light sources in plant growth or health monitoring systems. Compared with other visible‐spectrum OLEDs, however, research in the field of deep‐red OLEDs is not as advanced. In this work, three new types of dibenzofuran‐based host materials are developed as n‐type exciplex host partners. Combining these with the deep‐red iridium complex bis(2,3‐diphenylquinoxaline)iridium(dipivaloylmethane) ([(DPQ)2Ir(dpm)]) and N,N′‐di(naphalene‐1‐yl)‐N,N′‐diphenylbenzidine (α‐NPD) as a p‐type exciplex host partner, a highly efficient deep‐red OLED can be realized with a maximum external quantum efficiency (ηext,max) of over 16 % with Comission Internationale de l′Éclairge (CIE) coordinates of (0.71, 0.28). In addition, the effect of the doping concentration and the p/n ratio of the exciplex host on the efficiency and the lifetime of the OLEDs are investigated. Consequently, the optimized device exhibits a ηext,max of over 15 % and a six‐time longer lifetime operating at high brightness of 100 cd m−2 compared with other state‐of‐the‐art deep‐red OLEDs.

Achieving High‐Performance Pure‐Red Electrophosphorescent Iridium(III) Complexes Based on Optimizing Ancillary Ligands

“…[12] To improve the device efficiencies, an exciplex system was also employed as ah ost for 1F-Ir and 2F-Ir;t his was demonstrated to be useful for improving the performanceo ft he devices. [13] The mixture of 4,4',4''-tris(carbazol-9-yl)-triphenylamine (TCTA) and 2-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-1phenyl-1H-benzo[d]imidazole (PIM-TRZ), an exciplex system newly developed by our group, was considered as the cohost because of the high PL and EL efficiencies. [14] For energy transfer,T CTA/PIM-TRZ (weightr atio:1 :3) shows an exciplex emission (l em % 521 nm) overlapped with the absorption of 1F-Ir/ 2F-Ir to ensure the FRET process ( Figure S3 in the Supporting Information).…”

“…Host materials are also crucial for reaching ideal OLED performance because they govern some important aspects of device physics, for example, carrier transport and energy transfer . To improve the device efficiencies, an exciplex system was also employed as a host for 1F‐Ir and 2F‐Ir ; this was demonstrated to be useful for improving the performance of the devices . The mixture of 4,4′,4′′‐tris(carbazol‐9‐yl)‐triphenylamine (TCTA) and 2‐[3‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl]‐1‐phenyl‐1 H ‐benzo[ d ]imidazole (PIM‐TRZ), an exciplex system newly developed by our group, was considered as the cohost because of the high PL and EL efficiencies .…”

Imidazolyl‐Phenylcarbazole‐Based Host Materials and Their Use for Co‐host Designs in Phosphorescent OLEDs

“…[3] To effectively transfer the energy of the host to the guest material, energy level matching is a sticking point. [4] For example, the host materials used for the green (e. g., tris(2phenylpyridine)iridium(III), Ir(ppy) 3 ) [5] and red (e. g., bis(1phenylisoquinoline)(acetylacetonate)iridium(III), Ir(piq) 2 (acac)) [6] phosphorescent emitter require the highest occupied molecular orbitals (HOMOs) lower than À 5.3 eV, and the lowest unoccupied molecular orbitals (LUMOs) higher than À 2.9 and À 3.1 eV, respectively. [7] In addition to the requirement of a suitable E g , the host's triplet energy (E T ) must be higher than the guest's.…”

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

“…Dibenzofurans are important oxygen-containing heterocycles present in multiple natural products [1,2] and have broad applications in areas ranging from medicinal chemistry [1][2][3][4][5][6][7][8][9][10] to materials science [11]. Figure 1 presents a few examples of dibenzofuran-containing molecules.…”