Highly efficient red thermally activated delayed fluorescence materials based on a cyano-containing planar acceptor

Abstract

A highly efficient red thermally activated delayed fluorescence material was realized via the introduction of multiple acceptor units into a rigid backbone.

Highly Efficient Near-Infrared Thermally Activated Delayed Fluorescence Molecules via Acceptor Tuning: Theoretical Molecular Design and Experimental Verification

“…Fluorescent materials based on the principle of thermally activated delayed fluorescence (TADF) with 100% exciton utilization and >30% of the external quantum efficiency used in organic light-emitting diodes (OLEDs) are known as the “third-generation” organic electroluminescent material and have attracted an increasing level of attention of researchers. − TADF materials can be an attractive low-cost alternative to phosphorescent organometallic complexes containing expensive precious metals such as iridium and platinum, especially in OLED displays and solid-state lighting applications. − In the past decade, many successful cases of the synthesis and application of TADF materials were reported. In particular, the simple molecular design strategies with electron-donor (D) and electron-acceptor (A) frameworks were successful in developing blue and green TADF emitters. , However, the effective development of deep red (DR) or near-infrared (NIR) molecules that are widely used in the fields of communication, organic photovoltaics, night-vision displays, organic sensors, and NIR bioimaging is still an issue, because similar simple molecular design strategies face the challenge of fast nonradiative decay of singlet states for near-infrared emission (i.e., wavelength maxima of >700 nm). − According to the energy gap theorem, the nonradiation rate [ K nr ∝ α exp­(−βΔ E opt )] increases exponentially with a decrease in Δ E opt , seriously affecting the fluorescence efficiency (Φ F ) of the emitter during the conversion of the radiation excitons into photons. In addition, H-aggregation and strong intermolecular π–π stacking interactions are also the main reasons for the quenching of such molecules. − Therefore, the realization of efficient NIR-TADFs has been a challenging task.…”

Fluorinated dibenzo[a,c]-phenazine-based green to red thermally activated delayed fluorescent OLED emitters

“…All three compounds exhibit strong absorption bands at around 310 nm, which can be attributed to locally excited (LE) p-p* transitions of the donors and BP-F moieties, respectively. [24][25][26] Weaker and broad absorption bands are observed from 410 to 520 nm, which are assigned to ICT transitions from the donor units to the acceptor core. 27 This latter band is more intense for 2DTCz-BP-F (l abs = 440 nm, 21 Â 10 3 M À1 cm À1 ) compared to those of 2DMAC-BP-F (l abs = 415 nm, 3 Â 10 3 M À1 cm À1 ) and 2PXZ-BP-F (l abs = 476 nm, 3 Â 10 3 M À1 cm À1 ) as the DTCz groups adopt a less twisted conformation, leading to greater conjugation and greater oscillator strength for the ICT transitions in 2DTCz-BP-F, values that are corroborated by the DFT calculations (Fig.…”

Fluorinated Dibenzo[a,c]-phenazine-Based Green to Red Thermally Activated Delayed Fluorescent OLED Emitters

“…All three compounds exhibit strong absorption bands at around 310 nm, which can be attributed to locally excited (LE) ππ* transitions of the donors and BP-F moieties, respectively. 15,25,26 Weaker and broad absorption bands are observed from 410 to 520 nm, which are assigned to ICT transitions from…”