Access to the triplet excited states of organic chromophores

2020 ◽  
Vol 49 (17) ◽  
pp. 6122-6140 ◽  
Author(s):  
Devika Sasikumar ◽  
Athira T. John ◽  
Jeswin Sunny ◽  
Mahesh Hariharan
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Organic Chromophores ◽  
Triplet Excited States

Triplet excited states, ubiquitous in organic chromophores, can be accessed through various pathways. The feasibility of each pathway is determined by the molecular and electronic structures of the organic chromophores.

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.

Theoretical Studies on the Electronic Structures and Spectral Properties of Two Iridium(III) Complexes with Tetraphenylimidodiphosphinate Ligand

2013 ◽  
Vol 660 ◽  
pp. 35-39
Author(s):  
De Ming Han ◽  
Gang Zhang ◽  
Li Hui Zhao
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Spectral Properties ◽  
Emission Spectra ◽  
Electron Affinities ◽  
Geometrical Structures ◽  
Ligand Charge Transfer ◽  
Triplet Excited States ◽  
Homo Lumo ◽  
Theoretical Results

The geometrical structures, electronic structures, and spectral properties of two Ir(III) complexes with tetraphenylimidodiphosphinate ligand were investigated theoretically. The ground and the lowest lying triplet excited states were fully optimized at the B3LYP/LANL2DZ. TDDFT/PCM calculations have been employed to predict the absorption and emission spectra starting from the ground and excited state geometries, respectively. The lowest lying absorptions were calculated to be at 436 and 405 nm for the two Ir(III) complexes, respectively, and they have the transition configuration of HOMO → LUMO. The lowest lying transitions can be assigned as metal/ligand-to-ligand charge transfer (MLCT/LLCT) character for the two Ir(III) complexes. Ionization potentials (IP) and electron affinities (EA) were calculated to evaluate the injection abilities of holes and electrons. The theoretical results can be expected to provide valuable information to design new OLED materials.

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.

Unconventional singlet fission materials

2021 ◽  
Author(s):  
Tobias Ullrich ◽  
Dominik Munz ◽  
Dirk M. Guldi
Keyword(s):  
Excited States ◽  
Singlet Fission ◽  
Triplet Excited States

Singlet fission (SF) is a photophysical downconversion pathway, in which a singlet excitation transforms into two triplet excited states.

Different Quenching Effect of Intramolecular Rotation on the Singlet and Triplet Excited States of Bodipy

2017 ◽  
Vol 122 (1) ◽  
pp. 185-193 ◽  
Author(s):  
Zhangrong Lou ◽  
Yuqi Hou ◽  
Kepeng Chen ◽  
Jianzhang Zhao ◽  
Shaomin Ji ◽  
...  
Keyword(s):  
Excited States ◽  
Quenching Effect ◽  
Triplet Excited States ◽  
Intramolecular Rotation
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