Multicolor Luminescence Switching and Controllable Thermally Activated Delayed Fluorescence Turn on/Turn off in Carbazole–Quinoxaline–Carbazole Triads

Abstract

We report a series of thermally activated delayed fluorescence (TADF) molecules with mechanochromic luminescence properties and reversible TADF turn on/off properties in solid state that are induced by the transition between amorphous and crystalline states. Additionally, multicolor altering through external stimulus is demonstrated. All of the studied compounds exhibited recovery of the initial states associated with narrower emission spectra. TADF organic light-emitting diodes fabricated by solution processing rendered high external quantum efficiency up to 10.9% and luminance of 16 760 cd m.

Triphenylamine disubstituted naphthalene diimide: elucidation of excited states involved in TADF and application in near-infrared organic light emitting diodes

“…44 This means that within some conformations of the molecules there is significant orbital mixing between the donor and the acceptor units, forming a new molecular species. 45 Using the energy difference between the observed 1 CT state and a 3 LECon (a triplet state from the more conjugated planar molecular species) phosphorescence, the ΔES-T of TPA-cNDI in zeonex is found to be 180 meV, resulting in a rISC process that creates the observed delayed emission. The energy of the 3 LECon state will rise upon decrease of the conjugation to become identical with 3 LEA when the D and A species are perfectly orthogonal (note this refers to excited, not ground state geometry).…”

Recent Advancements in and the Future of Organic Emitters: TADF‐ and RTP‐Active Multifunctional Organic Materials

“…Dias, Grazulevicius, and co-workers developed an ew series of TADF-and multicolor-changing MCL organic materials based on aD -A-D scaffold that comprised aq uinoxaline as an acceptoru nit and functionalized carbazoles as donors (Figure 34 a). [110] Time-resolved spectroscopy revealed that the locally excited triplet state ( 3 LE) of these D-A-D compounds gradually shiftedtolower energy as the electron-donating ability of the installed donors increased in the order CzQX > tCzQx > MeOQx > MeO2Qx.T hisr esult indicatedt hat, even in these highlyt wisted D-A systems, the donor and acceptor did not completely decouple, but still interacted with each other, depending on the electron-donatinge ffect of the donor units. All of these materials showeda lternating emission colors in the solid states upon the applicationo fe xternal stimuli,s uch as grinding, heating, fuming, melting, and drop-casting (Figure 34 b).…”

Incorporating Thermally Activated Delayed Fluorescence into Mechanochromic Luminescent Emitters: High‐Performance Solution‐Processed Yellow Organic Light Emitting Diodes

“…Soon after, Minakata and co‐workers developed two TADF molecules that exhibit multicolor‐changing MCL by introducing phenothiazine as donors . Recently, Grazulevicius and co‐workers and co‐workers successfully synthesized four multifunctional MCL‐TADF luminogens, the external quantum efficiencies (EQEs) of resulting OLEDs reached 10.9% . Despite of these excellent works, the multicolor‐changing (not less than three colors) TADF materials, which look more promising in applications of security inks, information storage and sensors, are still limited due to the challenges in molecular design .…”