Interplay between Mixed and Pure Exciton States Controls Singlet Fission in Rubrene Single Crystals
Dmitry R Maslennikov1, Marios Maimaris1, Haoqing Ning1
1Department of Chemistry and Centre for Processible Electronics, Imperial College London, London W120BZ, U.K.
Journal of the American Chemical Society
|June 24, 2025
Summary
Singlet fission (SF) converts one singlet exciton into two triplet excitons, boosting solar cell efficiency. This study identifies key intermediates and pathways in rubrene, offering new strategies for photovoltaic materials.
Area of Science:
- Materials Science
- Photovoltaics
- Quantum Chemistry
Background:
- Singlet fission (SF) is a process where one singlet exciton (S) generates two triplet excitons (T).
- SF is crucial for overcoming the Shockley-Queisser efficiency limit in semiconductor photovoltaic cells.
- Identifying intermediate states in SF is challenging due to complex, fast dynamics.
Purpose of the Study:
- To elucidate and control the SF mechanism in high-purity rubrene single crystals.
- To identify SF intermediates by disentangling intrinsic dynamics from defect effects.
- To unify previous SF observations and models in rubrene.
Main Methods:
- Application of 14 fs–1 ms transient absorption spectroscopy.
- Utilizing high-purity rubrene single crystals.
- Analysis of ultrafast and temperature-dependent dynamics.
Main Results:
- Above-gap excitation directly forms a hybrid singlet/triplet-pair state [S/TT].
- This [S/TT] state rapidly (<100 fs) branches into singlet or triplet excitons.
- A slow, temperature-activated (48 meV) incoherent fission process follows [S/TT] relaxation to S.
Conclusions:
- The study reveals competing SF pathways and intermediates in rubrene.
- Findings unify previous SF models and observations.
- Provides alternative strategies for developing SF-enhanced photovoltaic materials.
Related Concept Videos
01:25Deactivation Processes: Jablonski Diagram
930
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
930
01:13¹H NMR: Complex Splitting
1.4K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
1.4K
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
2.7K
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
2.7K
01:08Spin–Spin Coupling Constant: Overview
1.0K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.0K
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
1.2K
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
1.2K
03:35Hybridization of Atomic Orbitals II
33.9K
sp3d and sp3d 2 Hybridization
33.9K