Featured
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Impact of non-equilibrium molecular packings on singlet fission in microcrystals observed using 2D white-light microscopy
Intermolecular coupling plays a critical role in singlet fission. Now, high-resolution 2D white-light spectroscopy has been used to map the presence of non-equilibrium molecular packing in single TIPS-pentacene microcrystals and characterize its effect on the dynamics of singlet fission.
- Andrew C. Jones
- , Nicholas M. Kearns
- & Martin T. Zanni
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Article |
Vibronically coherent ultrafast triplet-pair formation and subsequent thermally activated dissociation control efficient endothermic singlet fission
Singlet fission — the conversion of one singlet exciton into two triplet excitons, could improve the efficiency of photovoltaic devices — but its mechanism is still to be fully understood. Now, in films of TIPS-tetracene, it has been shown that the formation of the triplet pair state, which has been proposed to mediate singlet fission, is ultrafast and vibronically coherent in this endothermic fission system.
- Hannah L. Stern
- , Alexandre Cheminal
- & Richard H. Friend
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News & Views |
Singlet to triplet and back again
Spin-triplet excitations commonly migrate through direct electron exchange between neighbouring molecules. Now, experiments show that back-and-forth interconversion between spin-triplet and spin-singlet states can significantly speed up triplet migration in organic crystals.
- Sean T. Roberts
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Article |
Cooperative singlet and triplet exciton transport in tetracene crystals visualized by ultrafast microscopy
Understanding the interplay between singlet fission and exciton transport is important if singlet-fission materials are to be used for solar cell applications. Now, a cooperative singlet–triplet transport mechanism has been revealed through ultrafast transient absorption microscopy.
- Yan Wan
- , Zhi Guo
- & Libai Huang
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News & Views |
Crystal crosslinking
Solid-state perovskite solar cells have recently emerged and have already reached efficiencies of 20%. Now, a simple solution-processing step that crosslinks neighbouring perovskite grain surfaces has been found to increase their stability, an important issue for future potential commercialization.
- Licheng Sun
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News & Views |
Brighter pieces of the puzzle
Hybrid organic–inorganic lead halide perovskites have recently emerged as ground-breaking photovoltaic materials. A recent confocal fluorescence microscopy study now raises hopes that perovskite solar cells can reach efficiencies beyond the recent record of 20%.
- Udo Bach
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Article |
The energy barrier in singlet fission can be overcome through coherent coupling and entropic gain
Better understanding of the mechanisms of singlet fission may facilitate its implementation in solar cells, improving their efficiency. Although singlet fission in tetracene is endothermic, it is now observed not to be thermally activated; rather a quantum coherent process allows access to the higher-energy multi-exciton state, which then forms two triplet excitons through an entropic driving force.
- Wai-Lun Chan
- , Manuel Ligges
- & X-Y. Zhu
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Review Article |
Lessons from nature about solar light harvesting
Photosynthesis starts when light is absorbed and the associated excitation energy is directed to reaction centres by antenna complexes. The principles learned from studying these complexes are described in this Review, and provide the framework from which the authors suggest how to elucidate strategies for designing light-harvesting systems that route the flow of energy in sophisticated ways.
- Gregory D. Scholes
- , Graham R. Fleming
- & Rienk van Grondelle
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News & Views |
Out with both baby and bathwater
After two decades of research, the efficiency of dye-sensitized solar cells seems to have reached a plateau. Now, changing both electrolyte and dye opens up new opportunities that offer the hope that the efficiency ceiling can be broken.
- C. Michael Elliott
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Article |
High-efficiency dye-sensitized solar cells with ferrocene-based electrolytes
Dye-sensitized solar cells combining electrolytes based on the ferrocene/ferrocenium redox couple with a metal-free organic donor–acceptor sensitizer are reported to achieve a record 7.5% energy conversion efficiency, revealing the great potential of ferrocene-based electrolytes for future dye-sensitized solar cell applications.
- Torben Daeneke
- , Tae-Hyuk Kwon
- & Leone Spiccia
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Research Highlights |
Simply sterics
The performance of dye-sensitized solar cells that use non-conventional redox mediators has been improved by decreasing the steric bulk of the mediator while increasing that of the associated dye.
- Gavin Armstrong
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News & Views |
Capturing hot electrons
The efficiency of photovoltaic materials is compromised by their inability to capture all the energy absorbed when excited by high-energy photons. Such absorption creates 'hot' electrons, and now their transfer from excited lead selenide nanocrystals to an electron acceptor provides a necessary initial step towards tapping their 'lost' energy.
- Prashant V. Kamat
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News & Views |
Two electrons from one photon
The absorption of a single photon can cause the excitation of more than one electron, but the mechanism of this 'multi-exciton generation' process is elusive. Now, calculations on pentacene show that geometrical distortions and intermediate excited states assist in producing two excited electrons from one photon.
- Laurens D. A. Siebbeles
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Article |
An organic redox electrolyte to rival triiodide/iodide in dye-sensitized solar cells
Although the triiodide/iodide redox couple works efficiently in dye-sensitized solar cells it restricts functionality by absorbing visible light. Now, a disulfide/thiolate redox couple that has negligible absorption in the visible spectral range is presented, which in conjunction with a sensitized heterojunction, displays an efficiency of 6.4% under standard illumination test conditions.
- Mingkui Wang
- , Nathalie Chamberland
- & Michael Grätzel