A Novel Spiro[acridine‐9,9′‐fluorene] Derivatives Containing Phenanthroimidazole Moiety for Deep‐Blue OLED Application

Abstract

Typical π-π stacking and aggregation-caused quenching could be suppressed in the film-state by the spiro conformation molecular design in the field of organic light-emitting diodes (OLEDs). Herein, a novel deep-blue fluorescent material with spiro conformation, 1-(4-(tert-butyl)phenyl)-2-(4-(10-phenyl-10H-spiro[acridine-9,9'-fluoren]-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (SAF-BPI), was designed and synthesized. The compound consists of spiro-acridine-fluorene (SAF) as donor part and phenanthroimidazole (BPI) as acceptor part. Owing to the rigid SAF skeleton, this compound exhibits a high thermal stability with a glass transition temperature (T ) of 198 °C. The compound exhibits bipolar transporting characteristics demonstrated by the single-carrier devices. The non-doped OLEDs based on the SAF-BPI as the emitting layer shows maximum emission at 448 nm, maximum luminance of 2122 cd m , maximum current efficiency (CE) of 3.97 cd A , and a maximum power efficiency of 2.08 lm W . The chromaticity coordinate is stable at (0.15, 0.10) at the voltage of 7-11 V. The device shows a slow efficiency roll-off with CE of 3.35 and 2.85 cd A at 100 and 1000 cd m , respectively.

Alcohol‐Soluble Electron‐Transport Materials for Fully Solution‐Processed Green PhOLEDs

“…Power X‐ray diffraction (XRD) spectroscopy was used to investigate the crystallization properties and stability of the spin‐coated PBIPO film (Figure c–d). Both before and after annealing, the films show identical spectra to that of the glass substrate, thus implying that pPBIPO and mBPBIPO could form amorphous films by using the spin‐coating process . Furthermore, atomic force microscopy (AFM) was used to investigate the surface morphology of the spin‐coated PBIPO films (see the Supporting Information, Figure S6).…”

Asymmetrically twisted phenanthrimidazole derivatives as host materials for blue fluorescent, green and red phosphorescent OLEDs

“…2). The incorporation of side capping at N 23 and substituent at C 25 enhanced the degree of molecular distortion and suppresses the aggregation formation/π-π stacking in film which results amorphous film during fabrication 60 . These orthogonal dihedral angles confirmed the non-coplanar twisting conformation of ANSPI, PNSPI, ASPINC and PSPINC results in high quantum efficiency in film by restraining intermolecular interaction 61–64 .

Figure 1Potential energy scan of ANSPI, PNSPI, ASPINC and PSPINC.

Figure 2Molecular structure, ground state geometries with dihedral angles and Frontier molecular orbitals of ANSPI, PNSPI, ASPINC and PSPINC.

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Tailoring the molecular design of twisted dihydrobenzodioxin phenanthroimidazole derivatives for non-doped blue organic light-emitting devices

“…The introduction of a dihydrobenzodioxin group on the phenanthroimidazole unit could enhance the molecular distortion degree, thereby suppressing the formation of aggregation or π–π stacking in the solid state and forming an amorphous film (smooth and pinhole-free) during device fabrication. 44 The side capping of dihydrobenzodioxin at N23 was twisted with respect to the phenanthroimidazole frame with dihedral angles of 89.9° (1)/89.8° (2)/89.6° (3). The fused aryl group attached to the imidazole carbon atom (C25) was tilted at angles of 85.6° (1)/86.1° (2)/90.3° (3), and these dihedral angles confirmed the non-coplanar twisting configurations of 1–3.…”