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Electrical Detection of Singlet Fission in Single Crystal Tetracene Transistors
摘要： We present the electrical detection of singlet fission in tetracene by using a field-effect transistor (FET). Singlet fission is a photo-induced spin-dependent process, yielding two triplet excitons from the absorption of a single photon. In this study, we engineered a more deterministic platform composed of an organic single crystal FET rather than amorphous or polycrystalline FETs to elucidate spin-dependent processes under magnetic fields. Despite the unipolar operation and relatively high mobility of single crystal tetracene FETs, we were able to manipulate spin dependent processes to detect magnetoconductance (MC) at room temperature by illuminating the FETs and tuning the bias voltage to adjust majority charge carrier density and trap occupancy. In considering the crystalline direction and magnetic field interactions in tetracene, we show the MC response observed in tetracene FETs to be the result of the singlet fission process.
关键词： organic field effect transistors,singlet fission,magnetoconductance,single crystalline organic semiconductors
更新于2025-09-23 15:22:29
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Diphenylisobenzofuran Bound to Nanocrystalline Metal Oxides: Excimer Formation, Singlet Fission, Electron Injection, and Low Energy Sensitization
摘要： We report the photophysical properties of the dicarboxylated diphenylisobenzofuran dye (1) bound to nanocrystalline metal oxide surfaces. With increased surface loading of 1, emission from the films is significantly quenched but with a small amount of excimer emission at maximum surface loadings. Long-lived triplets were observed by ns TA spectroscopy that is consistent with singlet fission occurring on mesoporous ZrO2. The evolution of these triplets however could not be convincingly resolved by our sub-nanosecond TA spectroscopy. Dye-sensitized devices composed of 1 on a TiO2|Al2O3 core-shell structure exhibited an unusual decrease, increase, and then decrease in Jsc with respect to the thickness of Al2O3. In these films the Al2O3 acts as a tunneling barrier to slow electron injection from the singlet excited state such that singlet fission, and electron injection from the triplet state become competitive. Proof-of-principle self-assembled bilayer films that exhibit efficient triplet energy transfer from a low energy absorbing dye to 1 is demonstrated as another step towards a SF-based DSSC that can circumvent the Shockley-Queisser limit.
关键词： low energy sensitization,excimer formation,singlet fission,electron injection,diphenylisobenzofuran,nanocrystalline metal oxides
更新于2025-09-23 15:21:21
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Quantitative Sequential Photoenergy Conversion Process from Singlet Fission to Intermolecular Two-Electron Transfers Utilizing Tetracene Dimer
摘要： Singlet fission (SF) theoretically enables to perform the sequential photoenergy conversion process starting from the singlet state and leading to electron transfer (ET) with the radical ion pair quantum yield approaching 200%. Additionally, the long lifetime of the triplet state opens possibility for intermolecular ET process in diffusion-limited reaction. However, the quantitative two-electron transfer process through SF has yet to be reported. Herein we demonstrated the quantitative sequential process involving SF and leading to intermolecular two-electron transfers using 2,2’-biphenyl-bridged tetracene dimer (Tet-BP-Tet: SF and electron donor) and chloranil (Ch: electron acceptor). The high-yield and long-lived individual triplet excited states of Tet-BP-Tet by SF (ΦT = 175 ± 5% and τT = 0.29 ms) resulted in the quantitative two-electron transfer process (ΦET = 173 ± 5%) with Ch in benzonitrile.
关键词： chloranil,photoenergy conversion,tetracene dimer,electron transfer,Singlet fission
更新于2025-09-23 15:21:21
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A Pentacene-based Nanotube Displaying Enriched Electro/Photochemical Activities
摘要： We report the first synthesis of a pentacene-based nanotube displaying a tubular conformation in solution. The product possesses a triangular prismatic structure with three pentacene chromophores connected by a rigid, triangular backbone. Steady-state and time-resolved spectroscopic analyses revealed that the nanotube exhibits enriched electro/photochemical activities due to the close proximity of the three pentacene chromophores, which allows for efficient intramolecular singlet fission and long-lived triplet excitons.
关键词： photochemistry,pentacene,singlet fission,nanotube,triplet excitons,electrochemistry
更新于2025-09-23 15:21:01
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Direct vs Delayed Triplet Energy Transfer from Organic Semiconductors to Quantum Dots and Implications for Luminescent Harvesting of Triplet Excitons
摘要： Hybrid inorganic-organic materials such as quantum dots (QDs) coupled with organic semiconductors have a wide range of optoelectronic applications, taking advantage of the respective materials strengths. A key area of investigation in such systems is the transfer of triplet exciton states to and from QDs, which has potential applications in the luminescent harvesting of triplet excitons generated by singlet fission, in photocatalysis and photochemical upconversion. While the transfer of energy from QDs to the triplet state of organic semiconductors has been intensely studied in recent years, the mechanism and materials parameters controlling the reverse process, triplet transfer to QDs have not been well investigated. Here, through a combination of steady state and time-resolved optical spectroscopy we study the mechanism and energetic dependence of triplet energy transfer from an organic ligand (TIPS-tetracene carboxylic acid) to PbS QDs. Over and energetic range spanning from exothermic (-0.3 eV) to endothermic (+0.1 eV) triplet energy transfer we find that the triplet energy transfer to the QD occurs through a single step process with a clear energy dependence that is consistent with an electron exchange mechanism as described by Marcus-Hush theory. In contrast, the reverse process, energy transfer from the QD to the triplet state of the ligand does not show any energy dependence in the studied energy range, interestingly a delayed formation of the triplet state occurs relative to the quantum dots decay. Based on the energetic dependence of triplet energy transfer we also suggest design criteria for future materials systems where triplet excitons from organic semiconductors are harvested via QDs, for instance in light emitting structures or the harvesting of triplet excitons generated via singlet fission.
关键词： singlet fission,quantum dots,solar energy,photon multiplication,triplet energy transfer
更新于2025-09-23 15:19:57
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A method to detect triplet exciton transfer from singlet fission materials into silicon solar cells: Comparing different surface treatments
摘要： Singlet fission is one of the most promising routes to overcome the single-junction efficiency limit for solar cells. Singlet fission-enhanced silicon solar cells are the most desirable implementation, but transfer of triplet excitons, the product of singlet fission, into silicon solar cells has proved to be very challenging. Here, we report on an all optical measurement technique for the detection of triplet exciton quenching at semiconductor interfaces, a necessary requirement for triplet exciton or charge transfer. The method relies on the growth of individual, single-crystal islands of the singlet fission material on the silicon surface. The islands have different heights, and we correlate these heights to the quenching efficiency of triplet excitons. The quenching efficiency is measured by spatially resolved delayed fluorescence and compared to a diffusion–quenching model. Using silicon capped with a blocking thermal oxide and aromatic monolayers, we demonstrate that this technique can quickly screen different silicon surface treatments for triplet exciton quenching.
关键词： singlet fission,delayed fluorescence,surface treatments,triplet exciton transfer,silicon solar cells
更新于2025-09-23 15:19:57
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Efficient Singlet Fission in a Pentacene-Based Nanotube
摘要： Angew. Chem. Int. Ed. 2019, DOI: 10.1002/anie.201812976.
关键词： pentacenes,singlet fission,nanotubes
更新于2025-09-19 17:15:36
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Time dependent correlations of entangled states with nondegenerate branches and possible experimental realization using singlet fission
摘要： The spin-entangled exciton states produced by singlet fission provide an experimental route to generate entangled states with nondegenerate branches. Nondegenerate entangled pair states possess an internal "clock" that leads to quantum beating in various detected quantities. The implications of this internal clock for Bell’s inequality measurements and correlated particle detection are analyzed using two- and three-state spin models. In a Bell’s inequality experiment, we find that the choice of detection times can determine whether quantum or classical correlations are observed. The conditions under which the detection events could be time- or spacelike separated are analyzed in order to clarify how the temporal evolution of one particle can influence the time-dependent detection probability of the other. Possible routes to the detection of individual correlated triplet excitons are discussed, emphasizing both physical questions concerning the separation and propagation of triplet excitons over macroscopic distances and experimental challenges concerning decoherence, detection, and interpretation of the signals. We argue that spin-entangled triplet exciton states produced by singlet fission could provide a new way to probe entangled state detection and collapse, complementing schemes based on polarization-entangled photon states.
关键词： detection,Bell’s inequality,correlated particle detection,spin-entangled exciton states,nondegenerate branches,triplet excitons,quantum beating,singlet fission,decoherence
更新于2025-09-12 10:27:22
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An exciting boost for solar cells
摘要： A process called singlet fission has the potential to enhance the efficiency of solar cells. The mechanism has been difficult to implement in such devices, but experiments demonstrate a way forward.
关键词： efficiency,hafnium oxynitride,tetracene,solar cells,silicon solar cells,singlet fission
更新于2025-09-11 14:15:04
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Systematic control of the rate of singlet fission within 6,13-diphenylpentacene aggregates with PbS quantum dot templates
摘要： Lead chalcogenide quantum dots (QDs) are promising acceptors for photovoltaic devices that harness the singlet fission (SF) mechanism. The rate of singlet fission of polyacenes in the presence of QDs is a critical parameter in determining the performance of such devices. The present study demonstrates that the rates of SF in a pentacene derivative, 6,13-dipenylpentacene (DPP), are modulated by forming coaggregates with PbS QDs in aqueous dispersions. PbS QDs generally accelerate SF within DPP aggregates, and the extent of acceleration depends on the size of the QD. The average rate of SF increases from 0.074 ps-1 for DPP-only aggregates to 0.37 ps-1 within DPP-D co-aggregates for QDs with radius 2.2 nm, whereas co-aggregation with the smallest (r = 1.6 nm) and largest (r = 2.7 nm) QDs we tried only slightly change the SF rate. The rate variation is associated with (i) the density of surface ligands, which is influenced by the faceting of the PbS surface, and (ii) the local dielectric constant for the DPP. To accelerate SF, the ligands should be dense enough to provide sufficient affinity for DPP aggregates and effectively perturb the perpendicular alignment of DPP monomers within aggregates to increase the intermolecular coupling that promotes SF, but should not be too dense so as to form a low dielectric environment that disfavors SF. The study suggests that it is critical to consider the influence of the microenvironment of QD surface on photophysical processes when fabricating QD/organic hybrid devices.
关键词： pentacene,photovoltaic devices,PbS,quantum dots,singlet fission
更新于2025-09-11 14:15:04