Acridone-amine D-A-D thermally activated delayed fluorescence emitters with narrow resolved electroluminescence and their electrochromic properties

Unusual Excimer/Dimer Behavior of a Highly Soluble C,N Platinum(II) Complex with a Spiro-Fluorene Motif

In this work, we introduce a spiro-fluorene unit into a phenylpyridine (CN)-type ligand as a simple way to deplanarize the structure and increase the solubility of the final platinum(II)···complex. Using a spiro-fluorene unit, orthogonal to the main coordination plane of the complex, reduces intermolecular interactions, leading to increased solubility but without significantly affecting the ability of the complex to form Pt···Pt dimers and excimers. This approach is highly important in the design of platinum(II) complexes, which often suffer from low solubility due to their mainly planar structure, and offers an alternative to the use of bulky alkyl groups. The nonplanar structure is also beneficial for vacuum-deposition techniques as it lowers the sublimation temperature. Importantly, there are no sp3 hybridized carbon atoms in the cyclometalating ligand that contain hydrogens, the undesired feature that is associated with the low stability of the materials in OLEDs. The complex displays high solubility in toluene, ∼10 mg mL-1, at room temperature, which allows producing solution-processed OLEDs in a wide range of doping concentrations, 5-100%, and EQE up to 5.9%, with a maximum luminance of 7400 cd m-2. Concurrently, we have also produced vacuum-deposited OLEDs, which display luminance up to 32 500 cd m-2 and a maximum EQE of 11.8%.

Carbonyl-Containing Thermally Activated Delayed Fluorescence Emitters for Narrow-Band Electroluminescence

Carbonyl-containing derivatives show enduring vitality in the field of thermally activated delayed fluorescence (TADF) materials; they can realize high device efficiency by using both singlet and triplet excitons for electroluminescence. Recently, a system based on fused ketone/amine exhibited huge potential for constructing multi-resonance TADF (MR-TADF) emitters, which exhibit higher narrow-band emission than conventional TADF emitters with twisted donor-acceptor (D-A) structure. Herein, we summarize current research progress in both traditional and MR-type ketone derivatives with TADF characteristics for introducing the molecular design strategy of maintaining high device efficiency while keeping narrow-band emission profile. We hope this review can inspire the emergence of more high-performance narrow-band materials.

Electrochromic properties of pyrene conductive polymers modified by chemical polymerization

Pyrene is composed of four benzene rings and has a unique planar melting ring structure. Pyrene is the smallest condensed polycyclic aromatic hydrocarbon, and its unique structural properties have been extensively studied. Pyrene has excellent properties such as thermal stability, high fluorescence quantum efficiency and high carrier mobility. This paper mainly used thiophene, EDOT and triphenylamine groups to enhance the pyrene based π-conjugated system and control the molecular accumulation of organic semiconductors, and improve their charge transport performances. Five kinds of polymer were synthesized and correspondingly characterized. The five kinds of pyrene conductive polymer had outstanding properties in terms of solubility, fluorescence intensity and thermal stability, good film-forming properties, stable electrochromic properties and high coloring efficiency. The coloration efficiency (CE) of PPYTP was as high as 277 cm² C⁻¹, and the switching response time was short. The coloring time of PPYEDOT was 1.3 s and the bleaching time was 3.2 s. The lower impedance will also provide the possibility of such polymers being incorporated into electrochromic devices in the future. In short, the synthesized new pyrene conductive polymers will have wide application prospects in the field of electrochromic materials.

Pyrene is composed of four benzene rings and has a unique planar melting ring structure.