Photoexcited carrier relaxation dynamics in pentacene probed by ultrafast optical spectroscopy: Influence of morphology on relaxation processes

Thorsmølle, V. K.; Averitt, R. D.; Demšar, Jure; Smith, D. L.; Tretiak, Sergei; Martin, Richard L.; Chi, X.; Crone, B. K.; Ramirez, A. P.; Taylor, Antoinette J.

doi:10.1016/j.physb.2009.07.063

Cited by 23 publications

(67 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Third, given that the energy of D is approximately twice that of the triplet T 1 (E(D) ≈ 2 × E(T 1 )), D has sufficient energy to act as an intermediate in the singlet fission process. This is consistent with the observation that, in contrast to tetracene, triplet formation is not thermally activated in pentacene 3,4 . Finally, the photo-induced absorption onset at 1.2 eV (ref.…”

Section: Discussionsupporting

confidence: 93%

“…The second triplet state (T 2 ) is located 2.12 eV above the ground state and thus 1.24 eV above T 1 . The predicted energy of triplet-triplet absorption from T 1 therefore explains the observed photo-induced absorption onset at 1.2 eV (maximum at 1.45 eV) 3,4 . The dark ME state D, which is the first excited state of 1 A G symmetry and the lowest-energy ME state, is 0.19 eV higher in energy than twice the energy of the triplet T 1 at the ground-state geometry.…”

Section: Resultsmentioning

confidence: 62%

“…In contrast, this is not the case in tetracene, because E(S 1 ) is less than 2 × E(T 1 ) and consequently singlet fission is thermally activated [5][6][7] . In pentacene crystals, both magnetic field measurements 8 and long (.1 ns) photoinduced absorption lifetimes show that triplets are present after optical excitation 3,4 . The energy of this absorption matches our theoretically predicted triplet-triplet excitation (vide infra), further confirming the generation of triplets.…”

mentioning

confidence: 99%

“…Singlet fission has been observed in crystalline pentacene [2][3][4] and may also govern MEG in materials other than pentacene or other polyacenes. Any MEG process necessarily entails the formation of a multi-exciton (ME) quantum state following photoexcitation, so taking advantage of the fission process to design more efficient photovoltaic materials will require a detailed understanding of both the MEG mechanism and the precise nature of the participating ME states.…”

mentioning

confidence: 99%

“…The singlet excitons generated by photoexcitation of crystalline pentacene undergo rapid, temperature-independent fission into two triplet excitons [2][3][4] . The lowest optically allowed singlet excited state (S 1 ) of crystalline pentacene has an excitation energy of more than twice its triplet energy (E(S 1 ) .…”

mentioning

confidence: 99%

See 4 more Smart Citations

Singlet fission in pentacene through multi-exciton quantum states

2010

View full text Add to dashboard Cite

Multi-exciton generation-the creation of multiple charge carrier pairs from a single photon-has been reported for several materials and may dramatically increase solar cell efficiency. Singlet fission, its molecular analogue, may govern multiexciton generation in a variety of materials, but a fundamental mechanism for singlet fission has yet to be described. Here, we use sophisticated ab initio calculations to show that singlet fission in pentacene proceeds through rapid internal conversion of the photoexcited state into a dark state of multi-exciton character that efficiently splits into two triplets. We show that singlet fission to produce a pair of triplet excitons must involve an intermediate state that (i) has a multiexciton character, (ii) is energetically accessible from the optically allowed excited state, and (iii) efficiently dissociates into multiple electron-hole pairs. The rational design of photovoltaic materials that make use of singlet fission will require similar ab initio analysis of multi-exciton states such as the dark state studied here.A lthough the maximum efficiency of single-junction solar cells is limited to 31% (ref. 1), multi-exciton generation (MEG) may enable dramatically higher efficiencies. MEG produces multiple charge carrier pairs from single photons, whereas typical solar cells only produce one exciton per photon. Singlet fission, in which two triplets are created from one excited singlet state, is the molecular analogue of MEG and has the inherent advantage that because the generated charge carriers are triplets, the forbidden triplet to ground-state singlet transition would decrease carrier recombination rates, preserving higher efficiencies.Singlet fission has been observed in crystalline pentacene 2-4 and may also govern MEG in materials other than pentacene or other polyacenes. Any MEG process necessarily entails the formation of a multi-exciton (ME) quantum state following photoexcitation, so taking advantage of the fission process to design more efficient photovoltaic materials will require a detailed understanding of both the MEG mechanism and the precise nature of the participating ME states.The singlet excitons generated by photoexcitation of crystalline pentacene undergo rapid, temperature-independent fission into two triplet excitons 2-4 . The lowest optically allowed singlet excited state (S 1 ) of crystalline pentacene has an excitation energy of more than twice its triplet energy (E(S 1 ) . 2 × E(T 1 )), making unactivated singlet fission energetically possible. In contrast, this is not the case in tetracene, because E(S 1 ) is less than 2 × E(T 1 ) and consequently singlet fission is thermally activated [5][6][7] . In pentacene crystals, both magnetic field measurements 8 and long (.1 ns) photoinduced absorption lifetimes show that triplets are present after optical excitation 3,4 . The energy of this absorption matches our theoretically predicted triplet-triplet excitation (vide infra), further confirming the generation of triplets. The observed yield of triple...

show abstract

Section: Discussionsupporting

confidence: 93%

Section: Resultsmentioning

confidence: 62%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Singlet fission in pentacene through multi-exciton quantum states

2010

View full text Add to dashboard Cite

show abstract

Lowest Singlet Exciton in Pentacene: Modern Calculations versus Classic Experiments

Pac

Petelenz

2014

ChemPhysChem

View full text Add to dashboard Cite

Based on simple model calculations, the expected magnitude of the field-induced shift observable in electroabsorption is estimated for three alternative assignments proposed in the literature for the lowest singlet excitation of the pentacene crystal (pure Frenkel exciton, pure charge-transfer exciton, or a mixture of both). The results are compared with the corresponding experimental value, which is also known from the literature. The latter turns out to be compatible only with the mixed parentage of the pertinent state, which contains the charge-transfer contribution in the range from 25 to 70%. The conclusion is discussed in the context of the present controversies concerning the existing experimental and theoretical evidence on this subject.

show abstract

Simple Evaluation of Singlet Fission Couplings for Interacting Dimer Systems

Sun

Huang

Cheng

2022

J Chinese Chemical Soc

View full text Add to dashboard Cite

Singlet fission (SF) could potentially generate two triplet excitations from the absorption of a single photon, which can be applied to significantly enhance the energy conversion efficiency of solar cells. Efficiency of SF for molecular dimers depend on couplings between electronic configurations, however, available theoretical methods for quantitative evaluations of these couplings often require high computational cost and thus it is still difficult to explore geometrical dependence of SF performance for molecular dimers. Herein, we present a direct derivation of the couplings relevant to SF process on the basis of rigorously localized dimeric orbitals. We then systematically show that the SF rates can be correlated with a SF overlap factor that can be easily evaluated from monomeric molecular orbitals. Furthermore, we demonstrate the validity of the overlap factor as a quantitative descriptor of effective SF coupling based on comparative studies on slip-stacked ethylene and tetracene dimers. With the validity confirmed, we applied the descriptor to investigate a large family of polycyclic aromatic hydrocarbons to reveal dimer geometries that could potentially exhibit highly efficient SF. Our results provide a theoretical tool that could significant increase the speed and reliability of the discovery process for efficient organic SF materials.

show abstract

Photoexcited carrier relaxation dynamics in pentacene probed by ultrafast optical spectroscopy: Influence of morphology on relaxation processes

Cited by 23 publications

References 30 publications

Singlet fission in pentacene through multi-exciton quantum states

Singlet fission in pentacene through multi-exciton quantum states

Lowest Singlet Exciton in Pentacene: Modern Calculations versus Classic Experiments

Simple Evaluation of Singlet Fission Couplings for Interacting Dimer Systems

Contact Info

Product

Resources

About