Photocatalytic activities of amorphous TiO2-Cr thin films prepared by magnetron sputtering

Huang, Jiamu; Li, Yuexia; Xiao-ping, Cai; Zhao, Piqi

doi:10.1007/s11595-007-5610-1

Cited by 19 publications

(25 citation statements)

References 6 publications

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“…We would therefore like to point out the importance to further examine the role played by the delocalized primary photoexcitation for charge generation in neat polymers. 50 We suggest that the electron and hole contributions of the excited state, less tightly bound during delocalization, might localize on different parts of the same chain or on neighbouring polymers. A branched pathway from the initially excited species can therefore lead to the formation of either neutral or charged states.…”

Section: 86-99mentioning

confidence: 83%

“…1C). 50 The relaxation of the short-lived delocalization is highly complex and originates from a number of entangled processes. Three main contributions to the dynamic localization have been identied by experimental and theoretical studies:…”

Section: 76mentioning

confidence: 99%

“…For example, conjugated polymers containing aromatic rings are typically torsionally disordered in the ground state, but tend to planarize in the excited state because the torsional potential is steeper. 50 This relaxation is largely responsible for the absence of mirror image symmetry and the large Stokes shi between the absorption and emission spectra of conjugated polymers and oligomers. The effects are much smaller in, for example, rigid ladder-type polymers, where torsional disorder is suppressed.…”

Section: 76mentioning

confidence: 99%

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Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

2013

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In this feature article, we review and examine evidence that the primary photoexcited species in conjugated polymers is considerably delocalized. Localization occurs via a series of complex relaxation mechanisms on the <200 femtosecond time scale. We show that short-lived delocalization in the neutral excited state and charge separated state of bulk heterojunction blends might play an essential role in ensuring efficient formation of free charge carriers for photovoltaic applications. Finally, the additional parameter of intramolecular charge transfer character in the excited state of more recently developed donor-acceptor copolymers is discussed. Both delocalization and partial charge transfer reduce the binding of the electron and hole in photoexcited organic semiconductors and can help to overcome the bottleneck to macroscopic current generation in polymer solar cells.

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Section: 86-99mentioning

confidence: 83%

Section: 76mentioning

confidence: 99%

Section: 76mentioning

confidence: 99%

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Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

2013

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“…17 Therefore, it is more likely that the decrease of r 0 involves localization of an initially delocalized excited state, caused by electronic relaxation through a manifold of delocalized states formed by coupling of the chromophoric units and/or by self-trapping of the exciton due to strong coupling to nuclear modes. 4,32,37,38 The former is expected to be predominant for PBDTTPD, as torsional self-trapping is limited. Higher energy excitation leads to population of higher-lying, more delocalized states, so that localization is more pronounced during relaxation, leading to greater loss of anisotropy within the time resolution and lower r 0 .…”

Section: ■ Introductionmentioning

confidence: 99%

Charge Separation Pathways in a Highly Efficient Polymer: Fullerene Solar Cell Material

Paraecattil

Banerji

2014

J. Am. Chem. Soc.

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PBDTTPD is one of the best conjugated polymers for solar cell applications (up to 8.5% efficiency). We have investigated the dynamics of charge generation in the blend with fullerene (PCBM) and addressed highly relevant topics such as the role of bulk heterojunction structure, fullerene excitation, and excess energy. We show that there are multiple charge separation pathways. These include electron transfer from photoexcited polymer, hole transfer from photoexcited PCBM, prompt (<100 fs) charge generation in intimately mixed polymer:fullerene regions (which can occur from hot states), as well as slower electron and hole transfer from excitons formed in pure PBDTTPD or PCBM domains (diffusion to an interface is necessary). Very interestingly, all the charge separation pathways are highly efficient. For example, the yield of long-lived carriers is not significantly affected by the excitation wavelength, although this changes the fraction of photons absorbed by PCBM and the amount of excess energy brought to the system. Overall, the favorable properties of the PBDTTPD:PCBM blend in terms of morphology and exciton delocalization allow excellent charge generation in all circumstances and strongly contribute to the high photovoltaic performance of the blend. ■ INTRODUCTIONOrganic solar cells based on electron-donating conjugated polymers blended with electron-accepting fullerene derivatives have reached high efficiencies beyond 8%.1−3 In order to further enhance their performance, it is essential to deeply understand the underlying photophysical processes. Highly relevant topics that need to be addressed include the role of delocalization and exciton diffusion for efficient charge generation at the donor:acceptor interface, the role of hot neutral and charge transfer states in the formation of free carriers, and the role of the fullerene as light harvester.4 Both the nanoscale structure of the bulk heterojunction (BHJ) and the photophysical dynamics must be considered to gain answers to those questions. Femtosecond transient absorption (TA) spectroscopy is an undeniably useful tool to study the dynamics of neutral excited states and photoinduced charges in the materials of interest. 5−9Here, we will show that this purely spectroscopic technique additionally yields detailed morphological insights. Our study leads to a comprehensive picture of how different charge generation pathways relate to BHJ structure.We focus the investigation on PBDTTPD (poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione), and its blend with PCBM ([6,6]-phenyl C 60 butyric acid methyl ester). The polymer is among the best performing for photovoltaic applications, with up to 8.5% efficiency.1 Recent reports on morphology control, 1,10−12 device design, 13 charge trapping, 14 long-term stability, 15 quantum calculations, 16,17 and spectroscopy 7,18−20 confirm high interest for the material. PBDTTPD also distinguishes itself from many other conjugated polymers through its very planar structure in both the ground and ex...

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“…Conjugated organic polymers having a conjugated main chain are expected to show such unique properties as electrical and photo-conductivity [1][2][3][4][5], migration and transfer of energy [6], gas permeability [7,8], optical nonlinearity [9,10], electrochromism [11], solvatochromism [12], fluorescent sensitizing [13], and lightemission [14][15][16][17][18]. Thereby, these materials are important as the active materials in a new generation of electronic and optical devices, including light-emitting devices [15,[19][20][21], photovoltaic cells [22,23], biological and chemical sensors [24,25], photo-detectors [26], optical lasers [27], field-effect transistors [28], and nonvolatile memory devices [29,30].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of a Water-Soluble Ionic Polyacetylene Derivative

et al. 2016

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A new water-soluble ionic polyacetylene was synthesized by the acid-catalyzed polymerization of 2-ethynylpyridine using acrylic acid. The polymerization proceeded well to give a high yield of polymer. The acetylenic C≡C bond stretching (2110 cm −1 ) and acetylenic ≡C-H bond stretching (3293 cm −1 ) peaks of 2-ethynylpyridine monomer were not seen in the FT-IR spectrum of polymer. The electro-optical and electrical properties of the ionic polyacetylene were measured and discussed. The resulting polymer showed strong maximum at 513 nm in the UV-Visible absorption, which is corresponding to photon energy of 2.42 eV. The energy gap width of polymer was estimated to be of 2.08 eV. It was observed that the electrochemical process of polymer is reproducible in the potential range of −1.80 to 1.60 V vs Ag/AgNO3. HOMO and LUMO levels of polymer were 4.85 eV and 2.77 eV, respectively.

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Photocatalytic activities of amorphous TiO2-Cr thin films prepared by magnetron sputtering

Cited by 19 publications

References 6 publications

Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

Charge Separation Pathways in a Highly Efficient Polymer: Fullerene Solar Cell Material

Synthesis and Characterization of a Water-Soluble Ionic Polyacetylene Derivative

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