Carbazole-2-carbonitrile as an acceptor in deep-blue thermally activated delayed fluorescence emitters for narrowing charge-transfer emissions

Abstract

This work reports a new acceptor for constructing donor-acceptor type (D-A type) blue thermally activated delayed fluorescence (TADF) emitters with narrowed charge-transfer (CT) emissions. A new acceptor core, carbazole-2-carbonitrile (CCN),...

A New Class of Donor‐π‐Acceptor Phosphonium Salt Exhibiting Intriguing Thermally Activated Delayed Fluorescence

“…It should be noted that broad emission is a typical characteristic of charge transfer in D-𝜋-A type of TADF fluorophores. [49,50] To explore the excited state relaxation process in BzDPP-Br, the excitation-wavelength-dependent PL spectra were carried out. It turned out that no shift was found in the PL spectra with excitation wavelength changing from 250 to 365 nm (Figure S5, Supporting Information).…”

Luminescent Complexes of Platinum, Iridium, and Coinage Metals Containing N-Heterocyclic Carbene Ligands: Design, Structural Diversity, and Photophysical Properties

“…Carbazole derivatives are important organic chromophores: they display rigid planar structure, strong donor ability, and rich photophysical and hole-transporting properties. ,,,, Owing to these properties, extensive attention has been devoted to preparing fluorescent molecules based on carbazoles for variety of applications including bioimaging probes. , In recent years, efforts were devoted to construct novel class of luminescent metal complexes containing carbazolates and amides as ligands in which the anionic N atom is bonded directly to the metal center. − As mentioned in this review, such molecules provide a platform where organic and inorganic chromophores are merged to generate novel excited states and hence it is expected to bring highly important electronic properties.…”

New strategy for developing deep blue TADF materials with narrow emission and CIEy < 0.06 employing host materials as donors

“…[6][7][8][9][10][11] Especially, narrow-emission TADF emitters have very important applications in ultra-highdefinition display panels. 12 However, efficient narrow-emission blue TADF emitters, especially narrow-emission deep blue TADF emitters with Commission International de l'Eclairage y coordinate (CIE y ) less than 0.1, still face many challenges. The main reasons are as follows: (i) high-energy emitters, host materials and transport layers are very rare, 13 (ii) long-lived triplet excitons affect the stability and efficiency roll-off of TADF-OLEDs, 14 (iii) a low RISC process of deep-blue materials causes exciton annihilation.…”

“…Generally, the narrow-emission materials are mainly conventional fluorescent molecules, resulting in internal quantum efficiency (IQE) being limited to only 25%. 12 Nowadays, to solve this problem, multi-resonant TADF (MR-TADF) compounds are an alternative class of materials, 17,18 which show narrowband emission with a FWHM of around 20-30 nm. However, they still have many deficiencies.…”

“…However, they still have many deficiencies. 12,17 For instance, compared with conventional D-A type TADF emitters, the stabilities of MR-TADF emitters are not sufficient because most MR-TADF emitters have long triplet lifetime and the RISC rates are typically slower. This limitation frequently leads to inefficient triplet harvesting and low performance of the OLEDs.…”