Search

A new family of thermally activated delayed fluorescence (TADF) emitters based on a twisted donor‐acceptor (D−A) dyad scaffold comprising of dihydrophenazasiline (D) and pyrido[2,3‐b]pyrazine (A) has been developed, and their properties have been investigated. Time‐resolved spectroscopic analysis in matrices revealed the detailed photophysical properties of the D−A compounds. These D−A compounds serve as the emitter for organic light‐emitting diodes (OLEDs), showing a moderate external quantum efficiency (EQE) up to 9% in CBP matrix. Furthermore, theoretical calculations uncovered the excited states nature of the developed TADF emitters. [ABSTRACT FROM AUTHOR]

Novel electron donor–acceptor–donor (D‐A‐D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7‐membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C2 insertion into well‐known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine‐core D‐A‐D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room‐temperature phosphorescence and triplet–triplet annihilation. Furthermore, electrochemical analysis suggested sigma‐dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results. [ABSTRACT FROM AUTHOR]

Previous work has reported the synthesis of donor-acceptor-donor molecules based on dibenzophenazine acceptor group, presenting thermally activated delayed fluorescent (TADF) properties and their application in the assembly of highly efficient electroluminescent devices. Herein, we focus on the characterisation of charge carrier species through UV-Vis-NIR spectroelectrochemical and potentiostatic EPR techniques, in addition to the investigation of electropolymerisation properties of some compounds depicted in this study. The promising electrochromic features of both small molecules and conjugated polymers led to the assembly and investigation of electrochromic devices, evidencing the materials' versatility, applied in such different approaches as electrochromic windows and electroluminescent devices. Furthermore, the assembled OLEDs provided high efficiencies, with small roll-off, EQEs up to 20.5 % and luminance values up to 85 000 cd/m 2 ., (© 2022 Wiley-VCH GmbH.)

Although bowl-shaped N-pyrrolic polycyclic aromatic hydrocarbons (PAHs) can achieve excellent electron-donating ability, their application for optoelectronics is hampered by typically low photoluminescence quantum yields (PLQYs). To address this issue, we report the synthesis and characterization of a series of curved and fully conjugated nitrogen-doped PAHs. Through structural modifications to the electron-accepting moiety, we are able to switch the mechanism of luminescence between thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP), and to tune the overall PLQY in the range from 9 % to 86 %. As a proof of concept, we constructed solid-state organic light-emitting diode (OLED) devices, which has not been explored to date in the context of concave N-doped systems being TADF/RTP emitters. The best-performing dye, possessing a peripheral trifluoromethyl group adjacent to the phenazine acceptor, exhibits yellow to orange emission with a maximum external quantum efficiency (EQE) of 12 %, which is the highest EQE in a curved D-A embedded N-PAH to date., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Novel electron donor-acceptor-donor (D-A-D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7-membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C 2 insertion into well-known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine-core D-A-D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room-temperature phosphorescence and triplet-triplet annihilation. Furthermore, electrochemical analysis suggested sigma-dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)