Ultrafast spectroscopy reveals singlet fission, ionization and excimer formation in perylene film.
04 Mar 2021-Scientific Reports (Springer Science and Business Media LLC)-Vol. 11, Iss: 1, pp 5220-5220
TL;DR: In this article, a spin-allowed Singlet Exititon Fission (SF) was studied in pure perylene film, where two triplet excitons are created from one singlet exciton.
Abstract: Singlet exciton fission (SF) is a spin-allowed process whereby two triplet excitons are created from one singlet exciton. This phenomenon can offset UV photon energy losses and enhance the overall efficiency in photovoltaic devices. For this purpose, it requires photostable commercially available SF materials. Excited state dynamics in pure perylene film, ease of commercial production, is studied by time-resolved fluorescence and femtosecond transient absorption techniques under different photoexcitation energies. In film, polycrystalline regions contain perylene in H-type aggregate form. SF takes place from higher excited states of these aggregates in ultrafast time scale < 30 fs, reaching a triplet formation quantum yield of 108%. Moreover, at λex = 450 nm singlet fission was detected as a result of two-quantum absorption. Other competing relaxation channels are excimer (1 ps) and dimer radical cation formation (< 30 fs). Excimer radiatively relaxes within 19 ns and radical cation recombines in 3.2 ns. Besides, exciton self-trapping by crystal lattice distortions occurs within hundreds of picosecond. Our results highlight potential of simple-fabricated perylene films with similar properties as high-cost single crystal in SF based photovoltaic applications.
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TL;DR: In this article , triplet-triplet annihilation upconversion (TTA-UC) was integrated with photocatalysis directly via a detergent-free ternary toluene/isopropanol/water microemulsion system.
5 citations
TL;DR: In this paper , a broad-band red/near-infrared (NIR) light harvesting and efficient charge separation in a semiconductor is integrated for the realization of high photocatalytic efficiency but remains a challenge.
Abstract: Integrating broad-band red/near-infrared (NIR) light harvesting and efficient charge separation in a semiconductor is a crucial prerequisite for the realization of high photocatalytic efficiency but remains a challenge. Here, we discover that eosin Y (EY) aggregates exhibit strong red/NIR-light harvesting induced by electronic couplings between adjacent EY molecules. Simultaneously, the aggregates are favorable for exciton dissociation and formation of charge-separation states, greatly inhibiting charge recombination. The quantum yield (QY) of EY aggregates for hydrogen production highly reaches 23.6% at 610 nm. More importantly, this general concept of aggregation-induced red/NIR-light photocatalysis was observed in a series of typical organic dyes (11 examples). Impressively, the QY of cobalt phthalocyanin aggregates for hydrogen production is calculated to be 17.2% at 800 nm, which is the highest value among NIR-light-driven H2-evolution systems (≥800 nm) ever reported. This study unlocks a fresh realm of artificial photosynthesis, which uses dye aggregates for red/NIR-light solar conversion.
4 citations
TL;DR: In this paper, a pyrido[3,2-g]quinoline derivative named LA17b has been synthesized, and its photodynamic relaxation processes in solvents and films were studied by time-resolved fluorescence and femtosecond transient absorption techniques.
Abstract: With the aim of constructing efficient photoelectric organic materials, a pyrido[3,2-g]quinoline derivative named LA17b has been synthesized, and its photodynamic relaxation processes in solvents and films were studied by time-resolved fluorescence and femtosecond transient absorption techniques. The steady-state fluorescence spectra show pronounced red-shift with the increase of the solvent polarity as well as in binary solvent hexane/ethanol by increasing ethanol concentration. However, the strong red-shift does not lead to quenching of the fluorescence. This is explained in terms of a twisted intramolecular charge transfer (TICT) state. The TICT state of LA17b in ethanol is highly emissive with a long fluorescence lifetime: 1.1 ns. TICT state was shown to play an important role in enhancement of intersystem crossing rate. TD-DFT calculations confirm the pathways of relaxation of locally excited state via TICT and triplet states. In films, the photodynamic properties are similar to that of LA17b in hexane and the TICT state vanishes due to the rigid environment. The obtained optical properties of this molecule suggest that it can be a promising candidate for various optoelectronic applications.
4 citations
TL;DR: In this article , microdroplets and thin films of imidazolium-based ionic liquids (ILs) of different sizes and shapes were used as confining agents for the formation of high-quality perylene crystals by vapor deposition.
Abstract: Microdroplets and thin films of imidazolium-based ionic liquids (ILs) of different sizes and shapes were used as confining agents for the formation of high-quality perylene crystals by vapor deposition. The...
3 citations
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TL;DR: Glotaran is introduced as a Java-based graphical user interface to the R package TIMP, a problem solving environment for fitting superposition models to multi-dimensional data which features interactive and dynamic data inspection and interactive viewing of results.
Abstract: In this work the software application called Glotaran is introduced as a Java-based graphical user interface to the R package TIMP, a problem solving environment for fitting superposition models to multi-dimensional data. TIMP uses a command-line user interface for the interaction with data, the specification of models and viewing of analysis results. Instead, Glotaran provides a graphical user interface which features interactive and dynamic data inspection, easier -- assisted by the user interface -- model specification and interactive viewing of results. The interactivity component is especially helpful when working with large, multi-dimensional datasets as often result from time-resolved spectroscopy measurements, allowing the user to easily pre-select and manipulate data before analysis and to quickly zoom in to regions of interest in the analysis results. Glotaran has been developed on top of the NetBeans rich client platform and communicates with R through the Java-to-R interface Rserve. The background and the functionality of the application are described here. In addition, the design, development and implementation process of Glotaran is documented in a generic way.
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TL;DR: This review outlines advances made in understanding the relationship between aggregate structure and photophysics when vibronic coupling and intermolecular charge transfer are incorporated.
Abstract: The electronic excited states of molecular aggregates and their photophysical signatures have long fascinated spectroscopists and theoreticians alike since the advent of Frenkel exciton theory almost 90 years ago. The influence of molecular packing on basic optical probes like absorption and photoluminescence was originally worked out by Kasha for aggregates dominated by Coulombic intermolecular interactions, eventually leading to the classification of J- and H-aggregates. This review outlines advances made in understanding the relationship between aggregate structure and photophysics when vibronic coupling and intermolecular charge transfer are incorporated. An assortment of packing geometries is considered from the humble molecular dimer to more exotic structures including linear and bent aggregates, two-dimensional herringbone and “HJ” aggregates, and chiral aggregates. The interplay between long-range Coulomb coupling and short-range charge-transfer-mediated coupling strongly depends on the aggregate ...
865 citations
TL;DR: Interference between the short- and long-range (Coulomb) couplings gives rise to a host of new aggregate types, referred to as HH, HJ, JH, and JJ aggregates, with distinct photophysical properties, which can be exploited for electronic materials design.
Abstract: ConspectusThe transport and photophysical properties of organic molecular aggregates, films, and crystals continue to receive widespread attention, driven mainly by expanding commercial applications involving display and wearable technologies as well as the promise of efficient, large-area solar cells. The main blueprint for understanding how molecular packing impacts photophysical properties was drafted over five decades ago by Michael Kasha. Kasha showed that the Coulombic coupling between two molecules, as determined by the alignment of their transition dipoles, induces energetic shifts in the main absorption spectral peak and changes in the radiative decay rate when compared to uncoupled molecules. In H-aggregates, the transition dipole moments align “side-by-side” leading to a spectral blue-shift and suppressed radiative decay rate, while in J-aggregates, the transition dipole moments align “head-to-tail” leading to a spectral red-shift and an enhanced radiative decay rate. Although many examples of ...
400 citations
TL;DR: A library of organic triplet sensitizers based on a single chromophore of boron-dipyrromethene (BODIPY) is proposed, paving the way for the design and applications in photovoltaics and upconversions, etc.
Abstract: Triplet-triplet annihilation (TTA) based upconversions are attractive as a result of their readily tunable excitation/emission wavelength, low excitation power density, and high upconversion quantum yield. For TTA upconversion, triplet sensitizers and acceptors are combined to harvest the irradiation energy and to acquire emission at higher energy through triplet-triplet energy transfer (TTET) and TTA processes. Currently the triplet sensitizers are limited to the phosphorescent transition metal complexes, for which the tuning of UV-vis absorption and T(1) excited state energy level is difficult. Herein for the first time we proposed a library of organic triplet sensitizers based on a single chromophore of boron-dipyrromethene (BODIPY). The organic sensitizers show intense UV-vis absorptions at 510-629 nm (e up to 180,000 M(-1) cm(-1)). Long-lived triplet excited state (τ(T) up to 66.3 μs) is populated upon excitation of the sensitizers, proved by nanosecond time-resolved transient difference absorption spectra and DFT calculations. With perylene or 1-chloro-9,10-bis(phenylethynyl)anthracene (1CBPEA) as the triplet acceptors, significant upconversion (Φ(UC) up to 6.1%) was observed for solution samples and polymer films, and the anti-Stokes shift was up to 0.56 eV. Our results pave the way for the design of organic triplet sensitizers and their applications in photovoltaics and upconversions, etc.
347 citations
298 citations