scholarly journals Multiple Resonance Deep-red Emitters with Hybridized π-bonding/ non-bonding Orbitals to Surpass the Energy Gap Law

2021 ◽  
Author(s):  
Yuewei Zhang ◽  
Dongdong Zhang ◽  
Tianyu Huang ◽  
Alexander Gillett ◽  
Yang Liu ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Near Infrared ◽  
Energy Gap ◽  
Light Emitting Diode ◽  
Resonance Effect ◽  
Infrared Region ◽  
Decay Rates ◽  
Quantum Yields ◽  
Multiple Resonance ◽  
Energy Gap Law

Abstract Efficient organic emitters in the deep-red to near infrared region are rare due to the ‘energy gap law’. Here, multiple boron (B)- and nitrogen (N)-atoms embedded polycyclic heteroaromatics featuring hybridized π-bonding/ non-bonding molecular orbitals are constructed, providing a way to overcome the above luminescent boundary. The introduction of B-phenyl-B and N-phenyl-N structures enhances the electronic coupling of those para-positioned atoms, forming restricted π-bonds on the phenyl-core for delocalized excited states and thus a narrow energy gap. The mutually ortho-positioned B- and N-atoms also induce a multiple resonance effect on the peripheral skeleton for the non-bonding orbitals, creating shallow potential energy surfaces to eliminate the high-frequency vibrational quenching. The corresponding deep-red emitters with peaks at 662 nm and 692 nm exhibit narrow full-width at half-maximums of 38 nm, high radiative decay rates of ~108 s-1, ~100% photo-luminance quantum yields and record-high maximum external quantum efficiencies of >28% in a normal planar organic light-emitting diode structure, simultaneously.

scholarly journals Overcome the Energy Gap Law in Near-Infrared Emissive Aggregates via Nonadiabatic Coupling Suppression

2021 ◽  
Author(s):  
Jie Xue ◽  
Jingyi Xu ◽  
Jiajun Ren ◽  
Qingxin Liang ◽  
Qi Ou ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Near Infrared ◽  
High Efficiency ◽  
Organic Materials ◽  
Energy Gap ◽  
Delayed Fluorescence ◽  
Decay Rates ◽  
Nonadiabatic Coupling ◽  
Innovative Strategy ◽  
Energy Gap Law

<p>The pursuing of purely organic materials with high-efficiency near-infrared (NIR) emissions is fundamentally limited by the large non-radiative decay rates (<i>k</i><sub>nr</sub>) governed by the energy gap law. Here, we demonstrated a feasible and innovative strategy by employing intermolecular charge-transfer (CT) aggregates (CTA) to realize high-efficiency NIR emissions via nonadiabatic coupling suppression. The formation of CTA engenders intermolecular CT in the excited states; thereby, not only reducing the electronic nonadiabatic coupling and contributing to small <i>k</i><sub>nr</sub> for high-efficiency NIR photoluminescence, but also stabilizing excited-state energies and achieving thermally activated delayed fluorescence for high-efficiency NIR electroluminescence. This work provides new insights into aggregates and opens a new avenue for organic materials to overcome the energy gap law and achieve high-efficiency NIR emissions.<br></p>

scholarly journals Overcome the Energy Gap Law in Near-Infrared Emissive Aggregates via Nonadiabatic Coupling Suppression

2021 ◽  
Author(s):  
Jie Xue ◽  
Jingyi Xu ◽  
Jiajun Ren ◽  
Qingxin Liang ◽  
Qi Ou ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Near Infrared ◽  
High Efficiency ◽  
Organic Materials ◽  
Energy Gap ◽  
Delayed Fluorescence ◽  
Decay Rates ◽  
Nonadiabatic Coupling ◽  
Innovative Strategy ◽  
Energy Gap Law

<p>The pursuing of purely organic materials with high-efficiency near-infrared (NIR) emissions is fundamentally limited by the large non-radiative decay rates (<i>k</i><sub>nr</sub>) governed by the energy gap law. Here, we demonstrated a feasible and innovative strategy by employing intermolecular charge-transfer (CT) aggregates (CTA) to realize high-efficiency NIR emissions via nonadiabatic coupling suppression. The formation of CTA engenders intermolecular CT in the excited states; thereby, not only reducing the electronic nonadiabatic coupling and contributing to small <i>k</i><sub>nr</sub> for high-efficiency NIR photoluminescence, but also stabilizing excited-state energies and achieving thermally activated delayed fluorescence for high-efficiency NIR electroluminescence. This work provides new insights into aggregates and opens a new avenue for organic materials to overcome the energy gap law and achieve high-efficiency NIR emissions.<br></p>

scholarly journals Inverted energy gap law for the nonradiative decay in fluorescent floppy molecules: larger fluorescence quantum yields for smaller energy gaps

2019 ◽  
Vol 6 (12) ◽  
pp. 1948-1954 ◽  
Author(s):  
Junqing Shi ◽  
Maria A. Izquierdo ◽  
Sangyoon Oh ◽  
Soo Young Park ◽  
Begoña Milián-Medina ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Energy Gap ◽  
Quantum Yields ◽  
Nonradiative Decay ◽  
Fluorescence Quantum Yields ◽  
Energy Gaps ◽  
Energy Gap Law ◽  
Solution Increase ◽  
Floppy Molecules ◽  
Franck Condon

The non-radiative decay of substituted dicyano-distyrylbenzenes in solution increase with the Franck–Condon energy, being opposite to the conventional energy gap law.

scholarly journals Effect of the Substitution Position on the Electronic and Solvatochromic Properties of Isocyanoaminonaphthalene (ICAN) Fluorophores

Molecules ◽  
2019 ◽  
Vol 24 (13) ◽  
pp. 2434 ◽  
Author(s):  
Sándor Lajos Kovács ◽  
Miklós Nagy ◽  
Péter Pál Fehér ◽  
Miklós Zsuga ◽  
Sándor Kéki
Keyword(s):  
Radiative Decay ◽  
Fluorescence Emission ◽  
Solvent Polarity ◽  
Decay Rates ◽  
Quantum Yields ◽  
Time Resolved Fluorescence ◽  
Solvatochromic Shift ◽  
Fluorescence Emission Spectra ◽  
Time Resolved ◽  
Donor And Acceptor

The properties of 1,4-isocyanoaminonaphthalene (1,4-ICAN) and 2,6-isocyanoaminonaphthalene (2,6-ICAN) isomers are discussed in comparison with those of 1,5-isocyanoaminonaphthalene (1,5-ICAN), which exhibits a large positive solvatochromic shift similar to that of Prodan. In these isocyanoaminonaphthalene derivatives, the isocyano and the amine group serve as the donor and acceptor moieties, respectively. It was found that the positions of the donor and the acceptor groups in these naphthalene derivatives greatly influence the Stokes and solvatochromic shifts, which decrease in the following order: 1,5-ICAN > 2,6-ICAN > 1,4-ICAN. According to high-level quantum chemical calculations, this order is well correlated with the charge transfer character of these compounds upon excitation. Furthermore, unlike 1,5-ICAN, the 1,4-ICAN and 2,6-ICAN isomers showed relatively high quantum yields in water, that were determined to be 0.62 and 0.21, respectively. In addition, time-resolved fluorescence experiments revealed that both the radiative and non-radiative decay rates for these three ICAN isomers varied unusually with the solvent polarity parameter ET(30). The explanations of the influence of the solvent polarity on the resulting steady-state and time-resolved fluorescence emission spectra are also discussed.

Theoretical study of the substituent effect controlling the radiative and non-radiative decay processes of platinum(ii) complexes

2017 ◽  
Vol 19 (34) ◽  
pp. 23532-23540 ◽  
Author(s):  
Wei Shen ◽  
Wenting Zhang ◽  
Chaoyuan Zhu
Keyword(s):  
Substituent Effect ◽  
Radiative Decay ◽  
Theoretical Study ◽  
Energy Gap ◽  
Organometallic Complexes ◽  
Relaxation Dynamics ◽  
Energy Gap Law ◽  
Triplet Triplet Annihilation

By taking into account the energy gap law, relaxation dynamics and triplet–triplet annihilation (TTA), six organometallic complexes are systematically investigated for possible non-radiative decay processes.

scholarly journals Shortwave-infrared (SWIR) emitters for biological imaging: a review of challenges and opportunities

Nanophotonics ◽  
2017 ◽  
Vol 6 (5) ◽  
pp. 1043-1054 ◽  
Author(s):  
Elijah Thimsen ◽  
Bryce Sadtler ◽  
Mikhail Y. Berezin
Keyword(s):  
Quantum Efficiency ◽  
Near Infrared ◽  
Materials Science ◽  
Energy Gap ◽  
Tissue Imaging ◽  
Quantum Yields ◽  
Electromagnetic Spectrum ◽  
Surrounding Matrix ◽  
Low Efficiency ◽  
Shortwave Infrared

AbstractShortwave infrared radiation (SWIR) is the portion of the electromagnetic spectrum from approximately 900 nm to 2500 nm. Recent advances in imaging systems have expanded the application of SWIR emitters from traditional fields in materials science to biomedical imaging, and the new detectors in SWIR opened an opportunity of deep tissue imaging. Achieving deep photon penetration while maintaining high resolution is one of the main objectives and challenges in bioimaging used for the investigation of diverse processes in living organisms. The application of SWIR emitters in biological settings is, however, hampered by low quantum efficiency. So far, photoluminescent properties in the SWIR region have not been improved by extending concepts that have been developed for the visible (400–650 nm) and near-infrared (NIR, 700–900 nm) wavelengths, which indicates that the governing behavior is fundamentally different in the SWIR. The focus of this minireview is to examine the mechanisms behind the low efficiency of SWIR emitters as well as to highlight the progress in their design for biological applications. Several common mechanisms will be considered in this review: (a) the effect of the energy gap between the excited and ground state on the quantum efficiency, (b) the coupling of the excited electronic states in SWIR emitters to vibrational states in the surrounding matrix, and (c) the role of environment in quenching the excited states. General strategies to improve the quantum yields for a diverse type of SWIR emitters will be also presented.

Optical and Photovoltaic Properties of CdS/Ag2S Quantum Dots Co-Sensitized-Solar Cells

2013 ◽  
Vol 761 ◽  
pp. 15-18 ◽  
Author(s):  
Auttasit Tubtimtae ◽  
Ming Way Lee
Keyword(s):  
Solar Cells ◽  
Quantum Dot ◽  
Near Infrared ◽  
Energy Gap ◽  
Photocurrent Density ◽  
Infrared Region ◽  
Open Circuit ◽  
Photovoltaic Properties ◽  
Different Characteristics ◽  
Sensitized Solar Cells

Subscript textWe present a co-sensitization of CdS/Ag2S quantum-dot as sensitizers for solar cells. The optical properties of single and double-layered quantum-dot conditions were monitored using UV-Vis spectrophotometer. The results show that the different characteristics of absorption spectra depended on the types of QDs, indicating to the different energy gap of each QDs deposited on TiO2 surface and the tunable absorption ranges of the sample of double-layered quantum-dot-sensitized TiO2 electrodes are broader and the absorption intensity are higher than the single-layered quantum-dot, attributed to the co-absorption of two QDs to the light and both CdS and Ag2S are activated in visible to near-infrared region (450-1100 nm). The photovoltaic data shows that the highest efficiency of 1.41% with a photocurrent density, Jsc of 20.6 mA/cm2, an open-circuit voltage, Voc of 0.32 V and a fill factor, FF of 21.3% were yielded by the sample of CdS(3)/Ag2S(4) as an optimum condition of dipping cycles for CdS and Ag2S under irradiance of 100 mW/cm2 (AM 1.5G).

scholarly journals Beating the Limitation of Energy Gap Law Utilizing Deep Red MR-TADF Emitter with Narrow Energy-Bandwidth

2020 ◽  
Author(s):  
Yuewei Zhang ◽  
Dongdong Zhang ◽  
Tianyu Huang ◽  
Guomeng Li ◽  
Chen Zhang ◽  
...  
Keyword(s):  
High Performance ◽  
Near Infrared ◽  
Energy Gap ◽  
Organic Light Emitting Diodes ◽  
Vibrational Coupling ◽  
Light Emitting ◽  
Radiative Processes ◽  
Energy Gap Law ◽  
Mr Effect ◽  
Peripheral Skeleton

<p><b>The development of high-performance deep red/near-infrared organic light-emitting diodes is hindered by strong non-radiative processes as governed by the energy gap law. </b><b>Herein, a novel BN-containing skeleton featuring linear N-π-N and B-π-B structure is developed, establishing partial </b><b>bonding/antibonding character on phenyl core for enhanced electronics coupling of para-positioned B atoms as well as N atoms to narrow energy gaps. Also, the remained MR effect on the peripheral skeleton to maintain the MR effect to minimize the bonding/ antibonding character and suppress vibrational coupling between S<sub>0</sub> and S<sub>1</sub>, thereby </b><b>fundamentally</b><b> overcoming the luminescent boundary set by the energy gap law. The target</b><b> molecules </b><b>R-BN and R-TBN exhibited extremely high</b><b> PLQYs of 100% with </b><b>emission wavelengths at 666 and 686 nm,</b><b> respectively. The narrow FWMHs of 38 nm observed also testify the effectiveness of vibronic suppression. The corresponding OLEDs afford</b><b> </b><b>record-high</b><b> EQEs over 28% with emission wavelength over 664 nm</b><b>. </b><b></b></p>

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