scholarly journals Computational investigation on the large energy gap between the triplet excited-states in acenes

RSC Advances ◽  
2017 ◽  
Vol 7 (43) ◽  
pp. 26697-26703 ◽  
Author(s):  
Y. Y. Pan ◽  
J. Huang ◽  
Z. M. Wang ◽  
D. W. Yu ◽  
B. Yang ◽  
...  
Keyword(s):  
Excited State ◽  
Excited States ◽  
Organic Materials ◽  
Energy Gap ◽  
Great Influence ◽  
Accurate Description ◽  
Large Energy ◽  
Computational Investigation ◽  
State Behavior ◽  
Triplet Excited States

Accurate description triplet excited states is a challenge of organic materials. In this work, we investigate excited state behavior of acenes. The results show that the symmetry of the transition orbital have a great influence on the energy gap.

scholarly journals Tuning the singlet-triplet energy gap: a unique approach to efficient photosensitizers with aggregation-induced emission (AIE) characteristics

2015 ◽  
Vol 6 (10) ◽  
pp. 5824-5830 ◽  
Author(s):  
Shidang Xu ◽  
Youyong Yuan ◽  
Xiaolei Cai ◽  
Chong-Jing Zhang ◽  
Fang Hu ◽  
...  
Keyword(s):  
Excited State ◽  
Excited States ◽  
Energy Gap ◽  
Intersystem Crossing ◽  
Triplet Excited State ◽  
Triplet Energy ◽  
Aggregation Induced Emission ◽  
Unique Approach ◽  
Triplet Excited States

The efficiency of the intersystem crossing process can be improved by reducing the energy gap between the singlet and triplet excited states (ΔEST), which offers the opportunity to improve the yield of the triplet excited state.

scholarly journals Theoretical investigation of the effects of various substituents on the large energy gap between triplet excited-states of anthracene

RSC Advances ◽  
2018 ◽  
Vol 8 (49) ◽  
pp. 27979-27987 ◽  
Author(s):  
Yu Dawei ◽  
Zhang Xiaojuan ◽  
Wang Zhiming ◽  
Yang Bing ◽  
Ma Yuguang ◽  
...  
Keyword(s):  
Excited States ◽  
Theoretical Investigation ◽  
Energy Gap ◽  
Large Energy ◽  
Organic Electroluminescent ◽  
Triplet Excited States

The utilization of excitons is key to the effectiveness of organic electroluminescent materials.

Photoinduced ligand dissociation follows reverse energy gap law: nitrile photodissociation from low energy 3MLCT excited states

2020 ◽  
Vol 56 (29) ◽  
pp. 4070-4073
Author(s):  
Lauren M. Loftus ◽  
Jeffrey J. Rack ◽  
Claudia Turro
Keyword(s):  
Excited State ◽  
Excited States ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Energy Gap ◽  
Low Energy ◽  
Transient Absorption Spectroscopy ◽  
Ligand Dissociation ◽  
Energy Gap Law

Transient absorption spectroscopy is used to show that stabilization of the 3MLCT excited state in a series of Ru(ii) complexes leads to decreased population of the 3LF state, but does not reduce the efficiency of photoinduced nitrile dissociation.

scholarly journals Orthogonally Aligned Cyclic BODIPY Arrays with Long-lived Triplet Excited States as Efficient Heavy-Atom-Free Photosensitizers

2021 ◽  
Author(s):  
Zhaoyang Zhu ◽  
Xue Zhang ◽  
Xing Guo ◽  
Qing-Hua Wu ◽  
Zhongxin Li ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Energy Transfer ◽  
Excited State ◽  
Excited States ◽  
Heavy Atom ◽  
Triplet Excited State ◽  
Transfer Processes ◽  
Excited State Lifetimes ◽  
Triplet Excited States

Photosensitizers with long triplet excited state lifetimes are key to their efficient electron transfer or energy transfer processes. Herein, we report a novel class of cyclic trimeric BODIPY arrays which...

scholarly journals Excited State Character of Cibalackrot-Type Compounds Interpreted in Terms of Hückel-Aromaticity: A Rational for Singlet Fission Chromophore Design

2021 ◽  
Author(s):  
Weixuan Zeng ◽  
Ouissam El Bakouri ◽  
Dariusz Szczepanik ◽  
Hugo Bronstein ◽  
Henrik Ottosson
Keyword(s):  
Excited State ◽  
Theoretical Analysis ◽  
Excited States ◽  
State Energy ◽  
Energy Levels ◽  
Singlet Fission ◽  
Excited State Energy ◽  
Organic Chromophores ◽  
Spin Populations ◽  
Triplet Excited States

The exact energies of the lowest singlet and triplet excited states in organic chromophores are crucial to their performance in optoelectronic devices. The possibility of utilizing singlet fission to enhance the performance of photovoltaic devices has resulted in a wide demand for tuneable, stable organic chromophores with wide S<sub>1</sub> – T<sub>1</sub> energy gaps (>1 eV). Cibalackrot-type compounds were recently considered to have favorably positioned excited state energies for singlet fission, and they were found to have a degree of aromaticity in the lowest triplet excited state (T<sub>1</sub>). This work reports on a revised and deepened theoretical analysis taking into account the excited state Hückel-aromatic (instead of Baird-aromatic) as well as diradical characters, with the aim to design new organic chromophores based on this scaffold in a rational way starting from qualitative theory. We demonstrate that the substituent strategy can effectively adjust the spin populations on the chromophore moieties and thereby manipulate the excited state energy levels. Additionally, the improved understanding of the aromatic characters enables us to demonstrate a feasible design strategy to vary the excited state energy levels by tuning the number and nature of Hückel-aromatic units in the excited state. Finally, our study elucidates the complications and pitfalls of the excited state aromaticity and antiaromaticity concepts, highlighting that quantitative results from quantum chemical calculations of various aromaticity indices must be linked with qualitative theoretical analysis of the character of the excited states.

scholarly journals Quantum annealing using vacuum states as effective excited states of driven systems

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Hayato Goto ◽  
Taro Kanao
Keyword(s):  
Excited State ◽  
Excited States ◽  
Energy Gap ◽  
Stable State ◽  
Vacuum State ◽  
Quantum Systems ◽  
Quantum Annealing ◽  
Nonadiabatic Transition ◽  
Vacuum States ◽  
Gap Closing

AbstractQuantum annealing, which is particularly useful for combinatorial optimization, becomes more powerful by using excited states, in addition to ground states. However, such excited-state quantum annealing is prone to errors due to dissipation. Here we propose excited-state quantum annealing started with the most stable state, i.e., vacuum states. This counterintuitive approach becomes possible by using effective energy eigenstates of driven quantum systems. To demonstrate this concept, we use a network of Kerr-nonlinear parametric oscillators, where we can start excited-state quantum annealing with the vacuum state of the network by appropriately setting initial detuning frequencies for the oscillators. By numerical simulations of four oscillators, we show that the present approach can solve some hard instances whose optimal solutions cannot be obtained by standard ground-state quantum annealing because of energy-gap closing. In this approach, a nonadiabatic transition at an energy-gap closing point is rather utilized. We also show that this approach is robust against errors due to dissipation, as expected, compared to quantum annealing started with physical excited (i.e., nonvacuum) states. These results open new possibilities for quantum computation and driven quantum systems.

scholarly journals Delayed Fluorescence from Inverted Singlet and Triplet Excited States for Efficient Organic Light-Emitting Diodes

2021 ◽  
Author(s):  
Daigo Miyajima ◽  
Naoya Aizawa ◽  
Yong-Jin Pu ◽  
Atsuko Nihonyanagi ◽  
Ryotaro Ibuka ◽  
...  
Keyword(s):  
Excited States ◽  
Light Emitting Diodes ◽  
Energy Gap ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Positive Energy ◽  
Light Emitting ◽  
Organic Light ◽  
Spin Singlet ◽  
Triplet Excited States

Abstract Hund’s multiplicity rule states that for a given electronic configuration, a higher spin state has a lower energy. Rephrasing this rule for molecular excited states predicts a positive energy gap between spin-singlet and spin-triplet excited states, which has been consistent with numerous experimental observations over almost a century. Here, we report a fluorescent molecule that disobeys Hund’s rule, possessing a negative singlet–triplet energy gap of –11 meV. The energy inversion of the singlet and triplet excited states results in delayed fluorescence with short time constants of 0.2 μs, which anomalously decrease with decreasing temperature due to the emissive singlet character of the lowest-energy excited state. Organic light-emitting diodes using this molecule exhibited a fast transient electroluminescence decay with a peak external quantum efficiency of 17%, demonstrating potential implications for optoelectronic devices, including displays, lighting, and lasers.

New excited state intramolecular proton transfer (ESIPT) dyes based on naphthalimide and observation of long-lived triplet excited states

2012 ◽  
Vol 48 (78) ◽  
pp. 9720 ◽  
Author(s):  
Jie Ma ◽  
Jianzhang Zhao ◽  
Pei Yang ◽  
Dandan Huang ◽  
Caishun Zhang ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Excited States ◽  
Intramolecular Proton Transfer ◽  
Triplet Excited States
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