Journal ArticleDOI
Ultrafast Dynamics of Exciton Fission in Polycrystalline Pentacene
Mark W. Wilson,Akshay Rao,Jenny Clark,R. Sai Santosh Kumar,Daniele Brida,Giulio Cerullo,Richard H. Friend +6 more
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TLDR
This direct demonstration that triplet generation is both rapid and efficient establishes multiple exciton generation by exciton fission as an attractive route to increased efficiency in organic solar cells.Abstract:
We use ultrafast transient absorption spectroscopy with sub-20 fs time resolution and broad spectral coverage to directly probe the process of exciton fission in polycrystalline thin films of pentacene. We observe that the overwhelming majority of initially photogenerated singlet excitons evolve into triplet excitons on an ∼80 fs time scale independent of the excitation wavelength. This implies that exciton fission occurs at a rate comparable to phonon-mediated exciton localization processes and may proceed directly from the initial, delocalized, state. The singlet population is identified due to the brief presence of stimulated emission, which is emitted at wavelengths which vary with the photon energy of the excitation pulse, a violation of Kasha’s Rule that confirms that the lowest-lying singlet state is extremely short-lived. This direct demonstration that triplet generation is both rapid and efficient establishes multiple exciton generation by exciton fission as an attractive route to increased effic...read more
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Journal ArticleDOI
Recent Advances in Singlet Fission
Millicent B. Smith,Josef Michl +1 more
TL;DR: The current state of the development of molecular structure design rules, based on first-principles theoretical considerations, is described along with initial examples of implementation.
Journal ArticleDOI
External Quantum Efficiency Above 100% in a Singlet-Exciton-Fission–Based Organic Photovoltaic Cell
Daniel N. Congreve,Jiye Lee,Nicholas J. Thompson,Eric Hontz,Shane R. Yost,Philip D. Reusswig,Matthias E. Bahlke,Sebastian Reineke,Troy Van Voorhis,Marc A. Baldo +9 more
TL;DR: In this article, the authors demonstrate organic solar cells that exploit singlet exciton fission in pentacene to generate more than one electron per incident photon in a portion of the visible spectrum.
Journal ArticleDOI
Aggregation-Induced Emission: New Vistas at the Aggregate Level
TL;DR: This review focuses on the new properties of materials endowed by molecular aggregates beyond the microscopic molecular level and hopes this review will inspire more research into molecular ensembles at/beyond mesoscale level and lead to the significant progresses in material science, biological science, etc.
Journal ArticleDOI
Observing the multiexciton state in singlet fission and ensuing ultrafast multielectron transfer.
Wai-Lun Chan,Manuel Ligges,Askat E. Jailaubekov,Loren G. Kaake,Luis Miaja-Avila,Xiaoyang Zhu +5 more
TL;DR: Using the model system of pentacene/fullerene bilayers and femtosecond nonlinear spectroscopies, the state ensuing from singlet fission is observed and it is found that multiple electron transfer from the ME state to the fullerene occurs on a subpicosecond time scale, which is one order of magnitude faster than that from the triplet exciton state.
Journal ArticleDOI
Polymer solar cells
TL;DR: Recent work to image and control nanostructure in polymer-based solar cells is reviewed, and very recent progress is described using the unique properties of organic semiconductors to develop strategies that may allow the Shockley–Queisser limit to be broken in a simple photovoltaic cell.
References
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Journal ArticleDOI
Detailed Balance Limit of Efficiency of p‐n Junction Solar Cells
TL;DR: In this article, an upper theoretical limit for the efficiency of p−n junction solar energy converters, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of holeelectron pairs is radiative as required by the principle of detailed balance.
Journal ArticleDOI
Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells.
Arthur J. Nozik,Matthew C. Beard,Joseph M. Luther,Matt Law,Randy J. Ellingson,Justin C. Johnson +5 more
TL;DR: The general principles of QD synthesis are summarized using InP as an example and applications of QDs and QD arrays in novel quantum dot PV cells, where multiple exciton generation from single photons could yield significantly higher PV conversion efficiencies are discussed.
Journal ArticleDOI
Multiple Exciton Collection in a Sensitized Photovoltaic System
TL;DR: A photoelectrochemical system composed of PbS nanocrystals chemically bound to TiO2 single crystals is used to demonstrate the collection of photocurrents with quantum yields greater than one electron per photon, which has implications for increasing the efficiency of photovoltaic devices by avoiding losses resulting from the thermalization of photogenerated carriers.
Journal ArticleDOI
Efficient thin-film organic solar cells based on pentacene/C60 heterojunctions
TL;DR: In this article, an efficient organic photovoltaic cell based on a heterojunction of pentacene and C60 was fabricated, which exhibited broad light-harvesting throughout the visible spectrum with a peak external quantum efficiency (EQE) of 58±4% at short-circuit condition.
Journal ArticleDOI
Observation of long-range exciton diffusion in highly ordered organic semiconductors
TL;DR: The findings indicate that the exciton diffusion bottleneck is not an intrinsic limitation of organic semiconductors and suggest that long-lived triplet excitons are indeed generated in molecular crystals by fission of singlets, and these triplets provide a significant contribution to the surface photocurrent generated in organic materials.
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