High stability and luminescence efficiency in donor–acceptor neutral radicals not following the Aufbau principle

  title={High stability and luminescence efficiency in donor–acceptor neutral radicals not following the Aufbau principle},
  author={Haoqing Guo and Qiming Peng and Xian-Kai Chen and Qinying Gu and Shengzhi Dong and E. W. Evans and Alexander J. Gillett and Xin Ai and Ming Zhang and Dan Credgington and Veaceslav Coropceanu and Richard H. Friend and Jean‐Luc Br{\'e}das and Feng Li},
  journal={Nature Materials},
  pages={977 - 984}
With their unusual electronic structures, organic radical molecules display luminescence properties potentially relevant to lighting applications; yet, their luminescence quantum yield and stability lag behind those of other organic emitters. Here, we designed donor–acceptor neutral radicals based on an electron-poor perchlorotriphenylmethyl or tris(2,4,6-trichlorophenyl)methyl radical moiety combined with different electron-rich groups. Experimental and quantum-chemical studies demonstrate… 
Understanding the luminescent nature of organic radicals for efficient doublet emitters and pure-red light-emitting diodes
It is shown that non-alternant systems are necessary to lift the degeneracy of the lowest energy orbital excitations; moreover, intensity borrowing from an intense high-lying transition by the low-energy charge-transfer excitation enhances the oscillator strength of the emitter.
Organic Neutral Radical Emitters: Impact of Chemical Substitution and Electronic-State Hybridization on the Luminescence Properties.
These findings underscore that hybridization of the emissive state with high-energy states can, in analogy with the intensity borrowing effect commonly invoked for radiative transitions, enhance as well the nonradiative decay rates.
Tuning the absorption spectra of electrochromic small molecular radicals through the bridge modulation.
  • Lirong Yu, M. Shi, Hong Meng
  • Physics, Materials Science
    Chemphyschem : a European journal of chemical physics and physical chemistry
  • 2021
This work demonstrates that manipulating the π bridge between the donor and acceptor in the DBA system is an effective pathway not only to tailor the ICT properties of materials at their neutral state, but also to tune the absorption characteristics of their radical anion state, which makes them very promising for applications in electroluminescent and electrochemical devices.
A Pure‐Red Doublet Emission with 90 % Quantum Yield: Stable, Colorless, Iodinated Triphenylmethane Solid
Red luminescence is found in off-white tris(iodoperchlorophenyl)methane (3I-PTMH ) crystals which is characterized by a high photoluminescence quantum yield (PLQY 91 %) and color purity (CIE
A ground-state-dominated magnetic field effect on the luminescence of stable organic radicals†
The role of the magnetic field dominantly affects the spin sublevel population of radical dimers in the ground states, and the spin degree of freedom of ground-state open-shell molecules is a new key for achieving magnetic-field-controlled molecular photofunctions.
Excited-State Dynamics of Non-Luminecent and Luminescent π-Radicals.
  • Y. Teki
  • Chemistry, Physics
  • 2019
This minireview focuses on the excited-state dynamics of both photostable non(weakly)-luminescent and luminescent π-radicals, which are located opposite to each other.
Efficient light-emitting diodes from organic radicals with doublet emission
Organic light-emitting diodes (OLEDs) with doublet-spin radical emitters have emerged as a new route to efficient display technologies. In contrast to standard organic semiconductors, radical
Intermolecular locking design of red thermally activated delayed fluorescence molecules for high-performance solution-processed organic light-emitting diodes
Design of high-performance red thermally activated delayed fluorescence (TADF) materials remains a great challenge owing to their small energy bandgaps with severe nonradiative decay for low luminous
Proton-induced Conversion from Non-Aufbau to Aufbau Electronic Structure of an Organic Radical with Turn-on Fluorescence
We report a donor-acceptor(D-A) type non-luminescent neutral radical, tris-2,4,6-trichlorophenylmethyl-N, N-dimethyl-9H-carbazol-3-amine(TTM-Cz-DMA). The results of cyclic voltammetry and quantum
A Simple Approach to Achieve Organic Radicals with Unusual Solid-State Emission and Extraordinary Stability
Herein, we report a simple approach to generate stableluminescent radicals in the presence of gentle UV irradiation. The newly generated radicalspecies are capable of emitting unusual red light with


Up to 100% Formation Ratio of Doublet Exciton in Deep-Red Organic Light-Emitting Diodes Based on Neutral π-Radical.
The results indicate that using partially reduced radical mixture as emitter may be a way to solve aggregation-caused quenching in radical-based OLEDs.
High-efficiency electroluminescence and amplified spontaneous emission from a thermally activated delayed fluorescent near-infrared emitter
Near-infrared organic light-emitting diodes and semiconductor lasers could benefit a variety of applications including night-vision displays, sensors and information-secured displays. Organic dyes
Efficient radical-based light-emitting diodes with doublet emission
Efficient action is demonstrated of radical-based OLEDs16, whose emission originates from a spin doublet, rather than a singlet or triplet exciton, whose efficiency limitations imposed by tripleT excitons are circumvented for doublets.
Organic Light-Emitting Diodes Using a Neutral π Radical as Emitter: The Emission from a Doublet.
The results pave a new way to obtain 100% internal quantum efficiency of OLEDs, in which an organic open-shell molecule, (4-N-carbazolyl-2,6-dichlorophenyl)bis(2,4-6-trichlor phenyl)methyl (TTM-1Cz) radical, is used as an emitter, to circumvent the transition problem of triplet.
A Stable Room-Temperature Luminescent Biphenylmethyl Radical.
A new stable room-temperature luminescent radical, (N-carbazolyl)bis(2,4,6-tirchlorophenyl)methyl radical (CzBTM), which has improved properties compared to the triphenylmethyl radicals and has potential application to circumvent the problem of triplet harvesting in traditional fluorescent OLEDs.
Highly Efficient Blue Electroluminescence Using Delayed-Fluorescence Emitters with Large Overlap Density between Luminescent and Ground States
The use of thermally activated delayed-fluorescence (TADF) allows the realization of highly efficient organic light-emitting diodes (OLEDs) and is a promising alternative to the use of conventional
Near-Infrared Electroluminescence and Low Threshold Amplified Spontaneous Emission above 800 nm from a Thermally Activated Delayed Fluorescent Emitter
Near-infrared (NIR) organic light-emitting devices have aroused increasing interest because of their potential applications such as information-secured displays, photodynamic therapy, and optical
Red organic light-emitting radical adducts of carbazole and tris(2,4,6-trichlorotriphenyl)methyl radical that exhibit high thermal stability and electrochemical amphotericity.
Synthesis and characterization of new carbazolyl derivatives with a pendant stable radical of the TTM (tris-2,4,6-trichlorophenylmethyl radical) series are reported and show electrochemical amphotericity being reduced and oxidized to their corresponding stable charged species.
Highly Fluorescent Open-Shell NIR Dyes: The Time-Dependence of Back Electron Transfer in Triarylamine-Perchlorotriphenylmethyl Radicals
Triarylamine-perchlorotriphenylmethyl radicals (TARA-PCTM) may be viewed as open-shell mixed valence donor−acceptor compounds that exhibit strong charge-transfer (CT) bands in the visible to NIR
Switching radical stability by pH-induced orbital conversion.
Changing radical stability by 3-4 orders of magnitude using pH-induced orbital conversion opens a variety of attractive industrial applications, including pH-switchable nitroxide-mediated polymerization, and it might be exploited in nature.