Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

Abstract

Organic compounds that show Thermally Activated Delayed Fluorescence (TADF) have become wildly popular as next generation emitters in organic light-emitting diodes (OLEDs), but since 2016, have received significant and increasing attention as photocatalysts.

Carbene-metal complexes as molecular scaffolds for construction of through-space TADF emitters

“…This disparity is attributed to the overcrowding-induced change in hybridization of the N atom in MeCbz ligand. In addition, 3 LE level in 3 and 4 is slightly destabilized and lays 0.04 eV higher, in theory providing a tool for energy level tuning.…”

“…8 In order to correctly analyze CT emission and avoid the possible contribution of carbazolide 3 LE phosphorescence, only the CT emission was accounted for, when estimating low-temperature ΦPL values. To do so, the PL intensities were collected in time-resolved mode, till the point, where the collected CT emission intensity did not show any further increase and no apparent contribution from 3…”

“…Among those, metal-free organic compounds exhibiting thermally activated delayed fluorescence (TADF) have received the most attention. 1,2 Beside the main focus for applications in organic light emitting diodes (OLEDs), these compounds have found an extensive use in photocatalysis 3 and time-resolved imaging. 4 The emission from triplet state in these materials is realized through a reverse intersystem crossing (rISC) process between T1 and S1 levels, provided that singlet-triplet energy gap (ΔEST) is sufficiently small to be overcome at room temperature.…”

“…The next evolutionary step of TADF emitters introduced so called intramolecular exciplexes, where through-space CT proceeds between covalently bound D and A fragments and through-bond electronic coupling is prevented by σbonding or multiple conformational twists. [9][10][11] While such conformationally rigid materials solve some of the previously mentioned issues, the SOC between 1 CT and 3 CT states is practically nonexistent due to almost identical orbital configurations and the attainment of a rapid spin flip is often reliant on the aid of closely located local excited triplet states ( 3 LE). 12 Hence through-space TADF emitters often suffer from low radiative rates (kr).…”

Efficient synthesis of polyfunctionalized carbazoles and pyrrolo[3,4-c]carbazoles via domino Diels–Alder reaction

“…Midostaurin and carvediol have been approved by the FDA for tumor therapy and treatment of congestive heart failure [8]. On the other hand, carbazole derivatives also have potential applications in optoelectronic materials, conducting polymers, and synthetic dyes [9][10][11]. Over the past decades, many efficient synthetic methodologies for functionalized carbazole derivatives have been successfully developed [12][13][14][15][16][17][18].…”