Competition between triplet pair formation and excimer-like recombination controls singlet fission yield

It has long been recognized that visible light harvesting in Peridinin–Chlorophyll–Protein is driven by the interplay between the bright (S 2 ) and dark (S 1 ) states of peridinin (carotenoid), along with the lowest-lying bright (Q y ) and dark (Q x ) states of chlorophyll- a . Here, we analyse a chromophore cluster in the crystal structure of Peridinin–Chlorophyll–Protein, in particular, a peridinin–peridinin and a peridinin–chlorophyll- a dimer, and present quantum chemical evidence for excited states that exist beyond the confines of single peridinin and chlorophyll chromophores. These dark multichromophoric states, emanating from the intermolecular packing native to Peridinin–Chlorophyll–Protein, include a correlated triplet pair comprising neighbouring peridinin excitations and a charge-transfer interaction between peridinin and the adjacent chlorophyll- a . We surmise that such dark multichromophoric states may explain two spectral mysteries in light-harvesting pigments: the sub-200-fs singlet fission observed in carotenoid aggregates, and the sub-200-fs chlorophyll- a hole generation in Peridinin–Chlorophyll–Protein.

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Competition between polaron pair formation and singlet fission observed in amorphous rubrene films

Physical Review B ◽

10.1103/physrevb.87.224202 ◽

2013 ◽

Vol 87 (22) ◽

Cited By ~ 32

Author(s):

Vygintas Jankus ◽

Edward W. Snedden ◽

Daniel W. Bright ◽

Erhan Arac ◽

DeChang Dai ◽

...

Keyword(s):

Pair Formation ◽

Singlet Fission

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Magnetic Field Effects on Triplet Pair Generated by Singlet Fission in an Organic Crystal: Application of Radical Pair Model to Triplet Pair

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.6b09570 ◽

2016 ◽

Vol 120 (49) ◽

pp. 27858-27870 ◽

Cited By ~ 22

Author(s):

Tomoaki Yago ◽

Kei Ishikawa ◽

Ryuzi Katoh ◽

Masanobu Wakasa

Keyword(s):

Magnetic Field ◽

Radical Pair ◽

Organic Crystal ◽

Magnetic Field Effects ◽

Singlet Fission ◽

Field Effects ◽

Pair Model ◽

Triplet Pair

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Porous Shape-Persistent Rylene Imine Cages with Tunable Optoelectronic Properties and Delayed Fluorescence

10.26434/chemrxiv.12957314.v1 ◽

2020 ◽

Author(s):

Hsin-Hua Huang ◽

Kyung Seob Song ◽

Alessandro Prescimone ◽

Rajesh Mannancherry ◽

Ali Coskun ◽

...

Keyword(s):

Excited State ◽

Electronic Properties ◽

Green Light ◽

Delayed Fluorescence ◽

Optoelectronic Properties ◽

Covalent Organic Frameworks ◽

Singlet Fission ◽

Triplet Pair ◽

Material Porosity

A simultaneous combination of porosity and tunable optoelectronic properties, common in covalent organic frameworks, are rare in shape-persistent organic cages. Yet, organic cages offer important molecular advantages, the solubility and modularity. Herein, we report the synthesis of a series of chiral imine organic cages with three built-in rylene units by means of dynamic imine chemistry and we investigate their textural and optoelectronic properties. Thereby we demonstrate that the synthesized rylene cages are porous, can be reversibly reduced at accessible potentials, and can absorb from UV up to green light. We also show that they preferentially adsorb CO2 over N2 and CH4 with a good selectivity. In addition, we discovered that the cage incorporating three perylene-3,4:9,10-bis(dicarboximide) units displays a delayed fluorescence, likely as a consequence of formation of a correlated triplet pair, the multiexciton state in singlet fission. Rylene cages thus represent a unique platform to investigate the effect of electronic properties on material porosity and, at the same time, to probe excited-state phenomena in the limit of vanishing interchromophore coupling. <br>

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Revealing the contest between triplet-triplet exchange and triplet-triplet energy transfer coupling in correlated triplet pair states in singlet fission

10.33774/chemrxiv-2021-5lhjx-v2 ◽

2021 ◽

Author(s):

Vibin Abraham ◽

Nicholas Mayhall

Keyword(s):

Energy Transfer ◽

Exchange Interaction ◽

Entangled State ◽

Separation Mechanism ◽

Singlet Fission ◽

Triplet Energy ◽

Triplet Pair ◽

Triplet Energy Transfer ◽

State 1 ◽

Pair State

Understanding the separation of the correlated triplet pair state 1(TT) intermediate is critical for leveraging singlet fission to improve solar cell efficiency. This separation mechanism is dominated by two key interactions: (i) the exchange interaction (K) between the triplets which leads to the spin splitting of the biexciton state into 1(TT),3(TT) and 5(TT) states, and (ii) the triplet-triplet energy transfer integral (t) which enables the formation of the spatially separated (but still spin entangled) state 1(T...T). We develop a simple ab initio technique to compute both the biexciton exchange (K) and biexciton transfer coupling. Our key findings reveal new conditions for successful correlated triplet pair state dissociation. The biexciton exchange interaction needs to be ferromagnetic or negligible to the triplet energy transfer for favourable dissociation. We also explore the effect of chromophore packing to reveal geometries where these conditions are achieved for tetracene.

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