Isomeric spiro-[acridine-9,9′-fluorene]-2,6-dipyridylpyrimidine based TADF emitters: insights into photophysical behaviors and OLED performances

Abstract

TADF molecules with various dipyridylpyrimidine acceptors are synthesized and exhibited a max. EQE of 14.1% for a non-doped OLED device architecture.

High-Efficiency Diphenylpyrimidine Derivatives Blue Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes

“…The EL spectra of all the devices show solely emission peaks with any shoulder peaks, which could be contributed to good color gamut OLEDs. However, the EL spectra 4,6-PhPMAF doped device is red-shifted compared to the PL spectra, as discussed in reported 2,6-PhPMAF material (Ganesan et al, 2018). In the spectra, the EL maximum peak of the device with 4,6-PhPMAF dopant exhibit 458-nm emission, which is blue shifted compared to those of 2,6-PhPMAF dopant of 471 nm.…”

“…Triplet energy levels and reduction potentials of various acceptor cyano-substituted pyrazines were reported with combined small singlet-triplet splitting and large fluorescence rate (Liu et al, 2019). This molecular design can be accomplished with acridine, carbazole, and phenoxazine as electron donor units and/or sulfone, phosphine oxide, dimesitylboryl, and polycyclic borazine as electron acceptor units (Ganesan et al, 2018). Furthermore, as way of improving efficiency by device engineering, introducing the dual delayed fluorescence in the host material exhibited the slow-efficiency roll-offs (Zhang et al, 2019).…”

“…In other groups, highly ordered morphology and horizontal transition dipole moment ratio of Pt(II)-based [Pt(fppz) 2 ] and spiro[acridine-9,9 ′ -fluorene] donor with varied pyridyl orientation have been reported. High horizontal transition dipole moment ratio in para-linked donor between the donor-acceptor orientation has been measured using angle-dependent photoluminescence (PL) measurement (Ganesan et al, 2018). In our previous TADF work, we found that an m-phenyl linker between the electrondonating and the electron-accepting units showed higher device efficiencies; analysis of scattered X-ray intensities revealed a weak overlap in the phenyl linker, as well as well-aligned structure in the horizontal direction compared to those of the p-phenyl linker (Sohn et al, 2017).…”

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

“…[30] Moreover, the carrier transport layers with wide triplet energy bandgaps could effectively restrict the exciton diffusion to the adjacent layers. [31] As a result, the EL spectra of the tested devices are nearly identical except for the slight shift shown on the right side of the spectral profiles, also reflected in their corresponding CIE coordinates. Figure 6(b) shows the J-V curves of the tested devices.…”

Electroluminescence performance of a series of fluorene/2,5‐di(2‐thienyl)‐1H‐pyrrole polymers

“…9 Fluorene derivatives have various advantages for OLED application because of their high electroluminescence (EL) efficiencies, high quantum yield of photoluminescence (PL), morphological superiority, high thermal stabilities, and ambipolar carrier transporting properties. [10][11][12][13] The fluorene molecule can be easily functionalized at its 9-position with long alkyl chain as a side moiety to bring in enhanced solubility into the rigid molecule. Furthermore, polyfluorene has an absorption band in the UV region, thus its emission spectrum covers the blue light zone.…”