scholarly journals Comparing Donor- and Acceptor-Originated Exciton Dynamics in Non-Fullerene Acceptor Blend Polymeric Systems

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1770
Author(s):  
Chan Im ◽  
Sang-Woong Kang ◽  
Jeong-Yoon Choi ◽  
Jongdeok An
Keyword(s):  
Flexible Electronics ◽  
Transient Absorption ◽  
Film Formation ◽  
Transient Absorption Spectroscopy ◽  
Excitation Wavelength ◽  
Polymeric Systems ◽  
Donor And Acceptor ◽  
Novel Material ◽  
Spectrally Resolved ◽  
Energy Strategies

Non-fullerene type acceptors (NFA) have gained attention owing to their spectral extension that enables efficient solar energy capturing. For instance, the solely NFA-mediated absorbing region contributes to the photovoltaic power conversion efficiency (PCE) as high as ~30%, in the case of the solar cells comprised of fluorinated materials, PBDB-T-2F and ITIC-4F. This implies that NFAs must be able to serve as electron donors, even though they are conventionally assigned as electron acceptors. Therefore, the pathways of NFA-originated excitons need to be explored by the spectrally resolved photovoltaic characters. Additionally, excitation wavelength dependent transient absorption spectroscopy (TAS) was performed to trace the nature of the NFA-originated excitons and polymeric donor-originated excitons separately. Unique origin-dependent decay behaviors of the blend system were found by successive comparing of those solutions and pristine films which showed a dramatic change upon film formation. With the obtained experimental results, including TAS, a possible model describing origin-dependent decay pathways was suggested in the framework of reaction kinetics. Finally, numerical simulations based on the suggested model were performed to verify the feasibility, achieving reasonable correlation with experimental observables. The results should provide deeper insights in to renewable energy strategies by using novel material classes that are compatible with flexible electronics.

Efficiency of Electron Injection in Dye-Sensitized Semiconductor Films

2010 ◽  
Vol 451 ◽  
pp. 79-95 ◽  
Author(s):  
Ryuzi Katoh ◽  
Akihiro Furube
Keyword(s):  
High Performance ◽  
Transient Absorption ◽  
Electron Injection ◽  
Transient Absorption Spectroscopy ◽  
Excitation Wavelength ◽  
Semiconductor Films ◽  
Nanocrystalline Films ◽  
Experimental Conditions ◽  
Nanocrystalline Tio2 ◽  
Dye Sensitized

The efficiency of electron injection (inj) in dye-sensitized nanocrystalline films has been studied by means of transient absorption spectroscopy. We observed inj of nearly unity for N3 dye adsorbed on nanocrystalline TiO2 films (N3/TiO2). We examined the effects of various experimental conditions, such as light intensity, excitation wavelength, and presence of additives (4-tert- butylpyridine, tBP and Li ions), on inj. We also used various semiconductors and sensitizer dyes to study the effect of free energy change (G) on inj. These results give us new insights for developing high-performance solar cell devices.

Single-shot transient absorption spectroscopy of an organic film

MRS Advances ◽  
2018 ◽  
Vol 3 (59) ◽  
pp. 3453-3457 ◽  
Author(s):  
Kelly S. Wilson ◽  
Madelyn N. Scott ◽  
Cathy Y. Wong
Keyword(s):  
Transient Absorption ◽  
Film Formation ◽  
Signal To Noise Ratio ◽  
Transient Absorption Spectroscopy ◽  
Organic Films ◽  
Single Shot ◽  
Organic Film ◽  
Pump Probe ◽  
Exciton Dynamics ◽  
Absorption Measurements

ABSTRACTWe report single-shot transient absorption (SSTA) measurements of an organic film of 3,3’-Diethyloxatricarbocyanine iodide (DOTCI). In SSTA, the pump-probe time delay is spatially encoded by using a tilted pump pulse. Translation of the sample during SSTA measurements averages over any spatial heterogeneity in the film. We demonstrate that exciton dynamics measured with the single-shot technique agrees with traditional transient absorption measurements of the same film. A signal-to-noise ratio of ∼40 is achieved in 10 s. The ability to measure exciton dynamics in organic films will enable future SSTA measurements of exciton dynamics during the molecular aggregation events that result in film formation.

scholarly journals Anti-Kasha Behavior of 3-Hydroxyflavone and Its Derivatives

2021 ◽  
Vol 22 (20) ◽  
pp. 11103
Author(s):  
Ka Wa Fan ◽  
Hoi Ling Luk ◽  
David Lee Phillips
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Transient Absorption ◽  
Intramolecular Proton Transfer ◽  
Transient Absorption Spectroscopy ◽  
Excitation Wavelength ◽  
Computational Studies ◽  
Femtosecond Transient Absorption ◽  
First Excited State ◽  
Experimental Findings

Excited state intramolecular proton transfer (ESIPT) in 3-hydroxyflavone (3HF) has been known for its dependence on excitation wavelength. Such a behavior violates Kasha’s rule, which states that the emission and photochemistry of a compound would only take place from its lowest excited state. The photochemistry of 3HF was studied using femtosecond transient absorption spectroscopy at a shorter wavelength excitation (266 nm), and these new experimental findings were interpreted with the aid of computational studies. These new results were compared with those from previous studies that were obtained with a longer wavelength excitation and show that there exists a pathway of proton transfer that bypasses the normal first excited state from the higher excited state to the tautomer from first excited state. The experimental data correlate with the electron density difference calculations such that the proton transfer process is faster on the longer excitation wavelength than compared to the shorter excitation wavelength.

scholarly journals Excitation Wavelength and Intensity-Dependent Multiexciton Dynamics in CsPbBr3 Nanocrystals

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 463
Author(s):  
Chaochao Qin ◽  
Zhinan Jiang ◽  
Zhongpo Zhou ◽  
Yufang Liu ◽  
Yuhai Jiang
Keyword(s):  
Auger Recombination ◽  
Transient Absorption ◽  
Photoluminescence Spectroscopy ◽  
Transient Absorption Spectroscopy ◽  
Excitation Wavelength ◽  
Time Resolved ◽  
Recombination Lifetime ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Femtosecond Transient Absorption

CsPbBr3 has attracted great attention due to unique optical properties. The understanding of the multiexciton process is crucial for improving the performance of the photoelectric devices based on CsPbBr3 nanocrystals. In this paper, the ultrafast dynamics of CsPbBr3 nanocrystals is investigated by using femtosecond transient absorption spectroscopy. It is found that Auger recombination lifetime increases with the decrease of the excitation intensity, while the trend is opposite for the hot-exciton cooling time. The time of the hot-carriers cooling to the band edge is increased when the excitation energy is increased from 2.82 eV (440 nm) to 3.82 eV (325 nm). The lifetime of the Auger recombination reaches the value of 126 ps with the excitation wavelength of 440 nm. The recombination lifetime of the single exciton is about 7 ns in CsPbBr3 nanocrystals determined by nanosecond time-resolved photoluminescence spectroscopy. The exciton binding energy is 44 meV for CsPbBr3 nanocrystals measured by the temperature-dependent steady-state photoluminescence spectroscopy. These findings provide a favorable insight into applications such as solar cells and light-emitting devices based on CsPbBr3 nanocrystals.

Thymine Dimerization Induced by Oxidative DNA Lesions and Epigenetic Intermediates via Triplet-Triplet Energy Transfer

2020 ◽  
Author(s):  
Mauricio Lineros-Rosa ◽  
Antonio Francés-Monerris ◽  
Antonio Monari ◽  
Miguel Angél Miranda ◽  
Virginie Lhiaubet-Vallet
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Dna Lesions ◽  
Transient Absorption Spectroscopy ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Dna Nucleobases

Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidative lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer the excitation energy to thymine-thymine dyads, inducing the formation of the highly toxic and mutagenic cyclobutane pyrimidine dimers (CPDs). By using steady-state and transient absorption spectroscopy, NMR, HPLC, and theoretical calculations, we quantify the differences in the triplet-triplet energy transfer mediated by ForU and ForC, revealing that the former is much more efficient in delivering the excitation energy and producing the CPD photoproduct. Although significantly slower than ForU, ForC is also able to harm DNA nucleobases and therefore this process has to be taken into account as a viable photosensitization mechanism. The present findings evidence a rich photochemistry crucial to understand DNA photodamage and of potential use in the development of biomarkers and non-conventional photodynamic therapy agents.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

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