Aromatic imide/amide-based organic small-molecule emitters for organic light-emitting diodes

Abstract

Aromatic imide/amide-based organic small molecules as emitters in organic light-emitting diodes have caught increasing attention. This study summarized their advances in terms of device performance and molecular design rules over the past 20 years.

Asymmetric D–A–D′ Scaffold inducing distinct mechanochromic luminescence

“…In both molecules, phthalimide is chosen as an electron-withdrawing acceptor (A) by virtue of its excellent stability, mechanical toughness, and rigid structure. 45 9H-carbazole (Cz) is employed as an end-capping electron-donating group due to its planar π conjugation and good charge transport ability. Distinguishing electron-donating units of pseudo-planar phenothiazine (PTZ) and propeller-like bis(4-(tert-butyl)phenyl)amine (tDPA) are used as the D' units make the molecular packing can be adjusted, eventually managing CzPL-PTZ and CzPL-tDPA parent cystals to exhibit distinct MCL.…”

Full-colour solvatochromic fluorescence emitted from a semi-aromatic imide compound based on ESIPT and anion formation

“…Such materials have been of great interest over the past few years [7,8]. In recent years, aromatic imide/amide molecules have attracted significant attention because of their excellent photothermal and chemical stabilities with rigid structures, high-fluorescence quantum yields, and characteristic electron-transporting properties [9]. Since the lowest energy electronic transition (LET) of phthalimide is a locally excited (LE) n-π* transition derived from a carbonyl group [10], phthalimide and N−alkylphthalimide exhibit only weak fluorescence with minimal oscillator strengths.…”

Improved performance of solution processed OLEDs using N-annulated perylene diimide emitters with bulky side-chains

“…Clearly by varying the sidechain of the PDI molecule, slight changes in OLED device performance are obtained. Compared to the literature the PDI based OLEDs have much improved performance 11,12 .…”

“…Kozma and coworkers appended large naphthyl moieties to the PDI chromophore and were able to achieve PLQY ~23% in the film and developed OLEDs based on these materials with moderate external quantum efficiency (EQE) of 0.6% 11 . The performance of OLEDs depends not only on the PLQY of the emitting layer but charge transport, radiative exciton formation efficiency, and light outcoupling efficiency 12 , thus completely isolating the PDI chromophore is not a option. A way to increase PLQY without sacrificing electrical performance is to control the aggregation of the PDI units via the formation of dimers, trimers, tetramers 13 .…”