Heteroatom oxidation controls singlet–triplet energy splitting in singlet fission building blocks

Blaskovits, J. Terence; Fumanal, Maria; Vela, Sergi; Cho, Yuri; Corminbœuf, Clémence

doi:10.1039/d1cc06755a

“…These hold inherently low triplet energies and have been identified as promising building blocks for SF. 29 , 32 , 34 , 35 , 50 , 51 The results show that 1 TT-to-2T 1 reaction energies follow opposite trends with respect to the vertical 5 TT– 1 TT splitting in a way that larger splitting results in less favorable 1 TT-to-2T 1 thermodynamics ( Figure 4 a) in agreement with the literature. 36 , 47 Thus, TT splitting can be used as the reference of TT dissociation energies.…”

Section: Resultssupporting

confidence: 89%

“…Indeed, a fundamental trade-off between the ability to display D-to-A CT S 1 and acceptor-local T 1 in coplanar copolymers was identified, 32 evidencing the need for accelerated design strategies to find promising SF candidates. 33 , 34 A comprehensive structure–property analysis of D–A copolymers allowed us to recognize the role of dihedral torsion in modulating and pushing the CT and local character of the excitations beyond the limit of the coplanar approach. 32 , 35 On the one side, a larger CT resulted in larger S 1 / 1 TT electronic coupling in a series of modified TDO-based copolymers, promoting fast S 1 -to- 1 TT dynamics.…”

Section: Introductionmentioning

confidence: 99%

Optimizing the Thermodynamics and Kinetics of the Triplet-Pair Dissociation in Donor–Acceptor Copolymers for Intramolecular Singlet Fission

Fumanal

¹

,

Corminbœuf

²

2022

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Singlet fission (SF) is a two-step process in which a singlet splits into two triplets throughout the so-called correlated triplet-pair ( 1 TT) state. Intramolecular SF (iSF) materials, in particular, have attracted growing interest as they can be easily implemented in single-junction solar cells and boost their power conversion efficiency. Still, the potential of iSF materials such as polymers and oligomers for photovoltaic applications has been partially hindered by their ability to go beyond the 1 TT intermediate and generate free triplets, whose mechanism remains poorly understood. In this work, the main aspects governing the 1 TT dissociation in donor–acceptor copolymers and the key features that optimize this process are exposed. First, we show that both thermodynamics and kinetics play a crucial role in the intramolecular triplet-pair separation and second, we uncover the inherent flexibility of the donor unit as the fundamental ingredient to optimize them simultaneously. Overall, these results provide a better understanding of the intramolecular 1 TT dissociation process and establish a new paradigm for the development of novel iSF active materials.

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“…The low yield of PD-CF3 in this process is associated with competitive formation of furan derivative (see Experimental Section). [53] The structures of PDs were confirmed by using 1 H NMR, 13 C NMR, and IR spectroscopy, MS spectrometry, and X-ray crystallography. Theoretical Study.…”

Section: Resultsmentioning

confidence: 99%

“…[6][7] Consequently, over the past several years, many experimental and theoretical investigations have been conducted to uncover new SF materials. [8][9][10][11][12][13][14][15][16][17][18][19][20] [21] To achieve the proper exergonicity for efficient SF, the singletexcited state energy level (ES, Fig. 1) of a substance must be higher than twice the energy level of its triplet-excited state (ET) (i.e., ES > 2ET).…”

Section: S1 + S0 ® [Tt] ® T1 + T1mentioning

confidence: 99%

Diphenyldihydropentalenediones: Potential Singlet Fission Materials with High Triplet Energy Levels

Nagaoka

¹

,

Matsui²,

Fuki

³

et al. 2022

Preprint

0

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2,2,5,5-Tetramethyl-3,6-diphenyl-2,5-dihydropentalene-1,4-dione (PD-H) was developed as a new molecular framework for singlet fission (SF) materials. It was proposed that PD-H and related substances would have high energy level of the triplet-excited state (ET) as a result of the enforcement of molecular planarity through incorporation of ring-fusion constrained diene and avoidance of resonance caused by the presence of amide moieties in the diketopyrrolopyrrole core. Three members of this family (PDs), PD-H, PD-OCH3 (the 4-methoxyphenyl derivative), and PD-CF3 (the 4-(trifluoromethyl)phenyl derivative), were synthesized. The results of photophysical studies revealed that the energy level of singlet-excited state (ES) and ET of PD-H are 2.88 and 1.43 eV, respectively. These values indicate that PD-H has the energy relationship, ES > 2ET, required for it to be a singlet fission material. Moreover, introduction of electron-donating or -withdrawing groups on the benzene rings in PD-H enable fine-tuning of ES and ET while maintaining ES > 2ET. The results of transient absorption spectroscopic studies show that PD-H, PD-OCH3, and PD-CF3 in CH2Cl2 have respective T1 lifetimes of 54, 94, and 108 microsec, which are long enough to utilize its triplet energy as an excitation energy in other optoelectronic systems. These findings suggest that diphenyldihydropentalenediones are potential candidates for SF materials with high ET levels.

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“…[6][7] Consequently, over the past several years, many experimental and theoretical investigations have been conducted to uncover new SF materials. [8,9,18,19,[10][11][12][13][14][15][16][17] To achieve the proper exergonicity for efficient SF, the singletexcited state energy level (ES, Fig. 1) of a substance must be higher than twice the energy level of its triplet-excited state (ET) (i.e., ES > 2ET).…”

Section: Introductionmentioning

confidence: 99%

Diphenyldihydropentalenediones: Potential Singlet Fission Materials with High Triplet Energy Levels

Nagaoka

¹

,

Matsui²,

Fuki

³

et al. 2022

Preprint

0

View full text Add to dashboard Cite

2,2,5,5-Tetramethyl-3,6-diphenyl-2,5-dihydropentalene-1,4-dione (PD-H) was developed as a new molecular framework for singlet fission (SF) materials. It was proposed that PD-H and related substances would have high energy level of the triplet-excited state (ET) as a result of the enforcement of molecular planarity through incorporation of ring-fusion constrained diene and avoidance of resonance caused by the presence of amide moieties in the diketopyrrolopyrrole core. Three members of this family (PDs), PD-H, PD-OCH3 (the 4-methoxyphenyl derivative), and PD-CF3 (the 4-(trifluoromethyl)phenyl derivative), were synthesized. The results of photophysical studies revealed that the energy level of singlet-excited state (ES) and ET of PD-H are 2.88 and 1.43 eV, respectively. These values indicate that PD-H has the energy relationship, ES > 2ET, required for it to be a singlet fission material. Moreover, introduction of electron-donating or -withdrawing groups on the benzene rings in PD-H enable fine-tuning of ES and ET while maintaining ES > 2ET. The results of transient absorption spectroscopic studies show that PD-H, PD-OCH3, and PD-CF3 in CH2Cl2 have respective T1 lifetimes of 54, 94, and 108 microsec, which are long enough to utilize its triplet energy as an excitation energy in other optoelectronic systems. These findings suggest that diphenyldihydropentalenediones are potential candidates for SF materials with high ET levels.

show abstract

Heteroatom oxidation controls singlet–triplet energy splitting in singlet fission building blocks

Abstract: Singlet fission (SF) is a promising multiexciton-generating process. Its demanding energy splitting criterion - that the S1 energy must be at least twice that of T1 - has limited the...

Cited by 12 publications

References 26 publications

Optimizing the Thermodynamics and Kinetics of the Triplet-Pair Dissociation in Donor–Acceptor Copolymers for Intramolecular Singlet Fission

Optimizing the Thermodynamics and Kinetics of the Triplet-Pair Dissociation in Donor–Acceptor Copolymers for Intramolecular Singlet Fission

Diphenyldihydropentalenediones: Potential Singlet Fission Materials with High Triplet Energy Levels

Diphenyldihydropentalenediones: Potential Singlet Fission Materials with High Triplet Energy Levels

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