| 1. |
- Boscolo Bibi, Sara, 1993-, et al.
(author)
-
Multi-spectroscopic study of electrochemically-formed oxide-derived gold electrodes
- 2024
-
In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 26:3, s. 2332-2340
-
Journal article (peer-reviewed)abstract
- Oxide-derived metals are produced by reducing an oxide precursor. These materials, including gold, have shown improved catalytic performance over many native metals. The origin of this improvement for gold is not yet understood. In this study, operando non-resonant sum frequency generation (SFG) and ex situ high-pressure X-ray photoelectron spectroscopy (HP-XPS) have been employed to investigate electrochemically-formed oxide-derived gold (OD-Au) from polycrystalline gold surfaces. A range of different oxidizing conditions were used to form OD-Au in acidic aqueous medium (H3PO4, pH = 1). Our electrochemical data after OD-Au is generated suggest that the surface is metallic gold, however SFG signal variations indicate the presence of subsurface gold oxide remnants between the metallic gold surface layer and bulk gold. The HP-XPS results suggest that this subsurface gold oxide could be in the form of Au2O3 or Au(OH)3. Furthermore, the SFG measurements show that with reducing electrochemical treatments the original gold metallic state can be restored, meaning the subsurface gold oxide is released. This work demonstrates that remnants of gold oxide persist beneath the topmost gold layer when the OD-Au is created, potentially facilitating the understanding of the improved catalytic properties of OD-Au.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- El-Zohry, Ahmed M., et al.
(author)
-
Highly Emissive Biological Bilirubin Molecules : Shedding New Light on the Phototherapy Scheme
- 2021
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 125:32, s. 9213-9222
-
Journal article (peer-reviewed)abstract
- Bilirubin (BR) is the main end-product of the hemoglobin catabolism. For decades, its photophysics has been mainly discussed in terms of ultrafast deactivation of the excited state in solution, where, indeed, BR shows a very low green emission quantum yield (EQY), 0.03%, resulting from an efficient nonradiative isomerization process. Herein, we present, for the first time, unique and exceptional photophysical properties of solid-state BR, which amend by changing the type of crystal, from a closely packed alpha crystal to an amorphous loosely packed beta crystal. BR alpha crystals show a very bright red emission with an EQY of ca. 24%, whereas beta crystals present, in addition, a low green EQY of ca. 0.5%. By combining density functional theory (DFT) calculations and time-resolved emission spectroscopy, we trace back this dual emission to the presence of two types of BR molecules in the crystal: a stiff monomer, M1, distorted by particularly strong internal H-bonds and a floppy monomer, M2, having a structure close to that of BR in solution. We assign the red strong emission of BR crystals to M1 present in both the alpha and beta crystals, while the low green emission, only present in the amorphous (beta) crystal, is interpreted as M2 emission. Efficient energy-transfer processes from M2 to M1 in the closely packed a crystal are invoked to explain the absence of the green component in its emission spectrum. Interestingly, these unique photophysical properties of BR remain in polar solvents such as water. Based on these unprecedented findings, we propose a new model for the phototherapy scheme of BR inside the human body and highlight the usefulness of BR as a strong biological fluorescent probe.
|
|
| 5. |
- El-Zohry, Ahmed M., et al.
(author)
-
Ultrafast transient infrared spectroscopy for probing trapping states in hybrid perovskite films
- 2022
-
In: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1
-
Journal article (peer-reviewed)abstract
- Studying the charge dynamics of perovskite materials is a crucial step to understand the outstanding performance of these materials in various fields. Herein, we utilize transient absorption in the mid-infrared region, where solely electron signatures in the conduction bands are monitored without external contributions from other dynamical species. Within the measured range of 4000 nm to 6000 nm (2500–1666 cm−1), the recombination and the trapping processes of the excited carriers could be easily monitored. Moreover, we reveal that within this spectral region the trapping process could be distinguished from recombination process, in which the iodide-based films show more tendencies to trap the excited electrons in comparison to the bromide-based derivatives. The trapping process was assigned due to the emission released in the mid-infrared region, while the traditional band-gap recombination process did not show such process. Various parameters have been tested such as film composition, excitation dependence and the probing wavelength. This study opens new frontiers for the transient mid-infrared absorption to assign the trapping process in perovskite films both qualitatively and quantitatively, along with the potential applications of perovskite films in the mid-IR region.
|
|
| 6. |
|
|
| 7. |
- Abdelhamid, Hani Nasser, et al.
(author)
-
Towards implementing hierarchical porous zeolitic imidazolate frameworks in dye-sensitized solar cells
- 2019
-
In: Royal Society Open Science. - : Royal Society Publishing. - 2054-5703. ; 6:7
-
Journal article (peer-reviewed)abstract
- A one-pot method for encapsulation of dye, which can be applied for dye-sensitized solar cells (DSSCs), and synthesis of hierarchical porous zeolitic imidazolate frameworks (ZIF-8), is reported. The size of the encapsulated dye tunes the mesoporosity and surface area of ZIF-8. The mesopore size, Langmuir surface area and pore volume are 15 nm, 960-1500 m(2). g(-1) and 0.36-0.61 cm(3). g(-1), respectively. After encapsulation into ZIF-8, the dyes show longer emission lifetimes (greater than 4-8-fold) as compared to the corresponding non-encapsulated dyes, due to suppression of aggregation, and torsional motions.
|
|
| 8. |
- Abdellah, Mohamed, et al.
(author)
-
Time-Resolved IR Spectroscopy Reveals a. Mechanism with TiO2 as a Reversible Electron Acceptor in a TiO2-Re Catalyst System for CO2 Photoreduction
- 2017
-
In: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 139:3, s. 1226-1232
-
Journal article (peer-reviewed)abstract
- Attaching the phosphonated molecular catalyst [(ReBr)-Br-I(bpy)-(CO)(3)](0) to the wide-bandgap semiconductor TiO2 strongly enhances the rate of visible-light-driven reduction of CO2 to CO in dimethylformamide with triethanolamine (TEOA) as sacrificial electron donor. Herein, we show by transient mid-IR spectroscopy that the mechanism of catalyst photoreduction is initiated by ultrafast electron injection into TiO2, followed by rapid (ps-ns) and sequential two-electron oxidation of TEOA that is coordinated to the Re center. The injected electrons can be stored in the conduction band of TiO2 on an ms-s time scale, and we propose that they lead to further reduction of the Re catalyst and completion of the catalytic cycle. Thus, the excited Re catalyst gives away one electron and would eventually get three electrons back. The function of an electron reservoir would represent a role for TiO2 in photocatalytic CO2 reduction that has previously not been considered. We propose that the increase in photocatalytic activity upon heterogenization of the catalyst to TiO2 is due to the slow charge recombination and the high oxidative power of the Re-II species after electron injection as compared to the excited MLCT state of the unbound Re catalyst or when immobilized on ZrO2, which results in a more efficient reaction with TEOA.
|
|
| 9. |
- Bi, Dongqin, et al.
(author)
-
Improved Morphology Control Using a Modified Two-Step Method for Efficient Perovskite Solar Cells
- 2014
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:21, s. 18751-18757
-
Journal article (peer-reviewed)abstract
- A two-step wet chemical synthesis method for methylammonium lead(II) triiodide (CH3NH3PbI3) perovskite is further developed for the preparation of highly reproducible solar cells, with the following structure: fluorine-doped tin oxide (FTO)/TiO2 (compact)/TiO2 (mesoporous)/CH3NH3PbI3/spiro-OMeTAD/Ag. The morphology of the perovskite layer could be controlled by careful variation of the processing conditions. Specifically, by modifying the drying process and inclusion of a dichloromethane treatment, more uniform films could be prepared, with longer emission lifetime in the perovskite material and longer electron lifetime in solar cell devices, as well as faster electron transport and enhanced charge collection at the selective contacts. Solar cell efficiencies up to 13.5% were obtained.
|
|
| 10. |
- Bi, Dongqin, et al.
(author)
-
Unraveling the Effect of PbI2 Concentration on Charge Recombination Kinetics in Perovskite Solar Cells
- 2015
-
In: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 2:5, s. 589-594
-
Journal article (peer-reviewed)abstract
- CH3NH3PbI3 perovskite solar cells have rapidly risen to the forefront of emerging photovoltaic technologies. A solution-based, two-step method was reported to enhance the reproducibility of these solar cells. In this method, first a coating of PbI2 is applied by spin-coating onto a TiO2-coated substrate, followed by a dip in a methylammonium iodide solution, leading to conversion to CH3NH3PbI3. The concentration of PbI2 in the spin-coating solution is a very important factor that affects the infiltration of the perovskite and the amount deposited. The best solar cell performance of 13.9% was obtained by devices prepared using 1.0 M of PbI2 in dimethylformamide. These devices also had the longest electron lifetime and shortest carrier transport time, yielding lowest recombination losses. Rapid quenching of the perovskite emission is found in device-like structures, suggesting reasonably good efficient carrier extraction at the TiO2 interface and quantitative extraction at the spiro-OMeTAD interface.
|
|
| 11. |
|
|
| 12. |
- El-Zohry, Ahmed M., et al.
(author)
-
Concentration and Solvent Effects on the Excited State Dynamics of the Solar Cell Dye D149 : The Special Role of Protons
- 2013
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:13, s. 6544-6553
-
Journal article (peer-reviewed)abstract
- D149 is one of the best-performing metal-free, organic dyes for dye-sensitized solar cells. Excited state lifetimes strongly depend on the solvent used and have previously been reported to be between 100 and 700 ps, without any mechanistic explanation being given. We have earlier shown that photo-isomerization is one of several deactivation processes. Here, we report that lifetimes in certain solvents depend on concentration, even in very dilute (nanomolar) solutions. A detailed investigation of the concentration dependence enables us to assign a second, faster deactivation channel besides isomerization that reduces lifetimes further: a ground-state, hydrogen-bonded 1:1 complex of D149 with acids or interaction with protic solvents leads to excited state quenching, most probably through excited state proton transfer. This includes self-quenching caused by D149's own carboxylic group through intermolecular interaction, accounting for the concentration-dependent lifetimes. We are now able to dissect the complex excited state behavior into its components, allowing us to attribute rate constants to the isomerization and the excited-state proton transfer process. We are also able to explain the excited state of D149 in a wide range of environmental conditions, in the presence of acids/bases, at different concentrations as well as with varying temperatures. Furthermore, we determine the barrier for isomerization, a thermally activated process. The consequences of these effects on solar cells are discussed. Also we show that ultrafast techniques like femtosecond pump probe and upconversion inherently do not provide the required responsiveness for work with the concentration ranges required here, whereas single photon counting with its ultimate sensitivity is able to resolve the underlying processes.
|
|
| 13. |
- El-Zohry, Ahmed M., et al.
(author)
-
Electron Dynamics in Dye-Sensitized Solar Cells Influenced by Dye-Electrolyte Complexation
- 2020
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:30, s. 16300-16307
-
Journal article (peer-reviewed)abstract
- Herein, we present the effect of ground-state complexation between organic photosensitizers and the utilized electrolyte in dye-sensitized solar cells. To do so, we selected a well-known standard organic dye, D149, and the traditional iodide/triiodide redox couple as a case study. First, we detected the ground-state interactions between the D149 dye and the electrolyte components in acetonitrile. These interactions in acetonitrile have been identified as well for the donor molecule of D149 and the ester form of D149. All of these ground-state complexes have relatively high binding constants in solution. In addition, a charge-transfer state has been detected for the [D149/I-2] complex in acetonitrile, giving long-lived species with a lifetime of more than hundreds of nanoseconds. The presence of these adsorbed complexes on semiconductor surfaces such as ZrO2 and TiO2 have been confirmed via steady-state absorption and time-resolved emission. More importantly, these complexes adsorb on the semiconductor surfaces, showing different electron dynamics on the TiO2 in comparison to the adsorbed D149 itself, in which the electron injection and recombination processes have been greatly modulated. Such formed complexes on the semiconductor surfaces can certainly limit the efficiency of a working solar cell based on similar organic dyes. Thus, attention to the structural design of the photosensitizers to avoid such formed complexes should be highlighted, which opens a new pathway for improving the solar cell efficiencies based on organic dyes.
|
|
| 14. |
- El-Zohry, Ahmed M.
(author)
-
Exploring Organic Dyes for Grätzel Cells Using Time-Resolved Spectroscopy
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- Grätzel cells or Dye-Sensitized Solar Cells (DSSCs) are considered one of the most promising methods to convert the sun's energy into electricity due to their low cost and simple technology of production. The Grätzel cell is based on a photosensitizer adsorbed on a low band gap semiconductor. The photosensitizer can be a metal complex or an organic dye. Organic dyes can be produced on a large scale resulting in cheaper dyes than complexes based on rare elements. However, the performance of Grätzel cells based on metal-free, organic dyes is not high enough yet. The dye's performance depends primarily on the electron dynamics. The electron dynamics in Grätzel cells includes electron injection, recombination, and regeneration. Different deactivation processes affect the electron dynamics and the cells’ performance.In this thesis, the electron dynamics was explored by various time-resolved spectroscopic techniques, namely time-correlated single photon counting, streak camera, and femtosecond transient absorption. Using these techniques, new deactivation processes for organic dyes used in DSSCs were uncovered. These processes include photoisomerization, and quenching through complexation with the electrolyte. These deactivation processes affect the performance of organic dyes in Grätzel cells, and should be avoided. For instance, the photoisomerization can compete with the electron injection and produce isomers with unknown performance. Photoisomerization as a general phenomenon in DSSC dyes has not been shown before, but is shown to occur in several organic dyes, among them D149, D102, L0 and L0Br. In addition, D149 forms ground state complexes with the standard iodide/triiodide electrolyte, which directly affect the electron dynamics on TiO2. Also, new dyes were designed with the aim of using ferrocene(s) as intramolecular regenerators, and their dynamics was studied by transient absorption.This thesis provides deeper insights into some deactivation processes of organic dyes used in DSSCs. New rules for the design of organic dyes, based on these insights, can further improve the efficiency of DSSCs.
|
|
| 15. |
- El-Zohry, Ahmed M., et al.
(author)
-
Ferrocene as a rapid charge regenerator in dye-sensitized solar cells
- 2016
-
In: Dyes and pigments. - : Elsevier. - 0143-7208 .- 1873-3743. ; 132, s. 360-368
-
Journal article (peer-reviewed)abstract
- Using the reductive power of the ferrocene moiety (Fc), an ultrafast regeneration step via a covalent attachment of a Fc moiety to an organic triphenylamine-based dye (L1) when adsorbed on TiO2 is highlighted. Two modified dyes with one and two Fc moieties attached (L1Fc, and L1Fc2), respectively, were synthesized by addition to the L1 dye. These dyes have been studied spectroscopically using ultrafast transient absorption spectroscopy in the visible and the infrared (IR) regions. In acetonitrile, the results show an ultrafast excited state quenching of the modified dyes due to an expected electron transfer process from the Fc(s) to L1. Adsorbed onto TiO2, an electron transfer process is also detected from Fc to the oxidized dye (L1(+)). Despite the occurrence of an ultrafast regeneration step, the solar cell performance does not improve by the attachment of Fc(s) to the dye L1. Transient absorption measurements in the IR region revealed a fast electron recombination process to the Fc(+) moiety on an average time scale of ca. 300 ps, outcompeting the >12 ns process to L1(+). The reasons for the observed considerably faster recombination rate to Fc(+) than to L1(+) are discussed in detail. This study provides deep spectroscopic insights for such organic dyes utilized to afford ultrafast regeneration step without showing high performance in photovoltaic devices. In addition, this study will improve our understandings for the triangular relationship between the molecular design, electron kinetics, and the performance in photovoltaic devices. (C) 2016 Elsevier Ltd. All rights reserved.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- El-Zohry, Ahmed M.
(author)
-
The origin of slow electron injection rates for indoline dyes used in dye-sensitized solar cells
- 2019
-
In: Dyes and pigments. - : ELSEVIER SCI LTD. - 0143-7208 .- 1873-3743. ; 160, s. 671-674
-
Journal article (peer-reviewed)abstract
- This work highlights the direct impact of selecting acceptor moiety for organic dyes on the electron dynamics at faster time scales, in which overlooked photo-physical properties are present on semiconductor surfaces with specific acceptor moieties. Four top-performing dyes of indoline family (D131, D102, D149, and D205) sharing the same donor moiety, but through different acceptor groups, were selected and compared with respect of electron injection process, using ultrafast transient-infrared probe. The presence of rhodanine moiety at the acceptor unit in D102, D149 and D205, shows an additional slow electron injection process, of picosecond time-scale, on the low band-gap semiconductor, TiO2. This slow process is expected to be present due to a twisted intramolecular charge transfer/isomerized state of the excited dye prior to electron injection. This isomerized state reduces as well the detrimental electron recombination process rates, and results of high performance in solar cells based on these rhodanine dyes. Replacing the rhodanine moiety by a cyano-acrylic group in D131 dye shows faster electron injection and recombination processes, due to the lower dipole moment present in the excited state, hindering the formation of an isomerized state. These findings will aid to enhance the organic dyes design used in dye sensitized solar cells, in which designed photo-physical processes on semiconductor surfaces can increase the efficiencies of the solar cells.
|
|
| 20. |
- El-Zohry, Ahmed M., et al.
(author)
-
Twisted Intramolecular Charge Transfer (TICT) Controlled by Dimerization : An Overlooked Piece of the TICT Puzzle
- 2021
-
In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 125:14, s. 2885-2894
-
Journal article (peer-reviewed)abstract
- Organic dyes have shown high efficiencies in solar cells, which is mainly attributed to the push-pull strategy present in such dyes upon attaching to the semiconductor surfaces. We deeply studied the fundamental photophysical properties of cyanoacrylic dyes, mostly the L1 dye, and found unique emission properties that depend on many factors such as the solvent polarity and the concentration of the dye and could present a complete emission picture about this family of dyes. The L1 dye shows an intramolecular charge transfer (ICT) emission state at low concentrations (approximately nanomolar scale) and shows a twisted intramolecular charge transfer (TICT) emission state in specific solvents upon increasing the concentration to the micromolar scale. Moreover, the associated emission lifetimes of the ICT and TICT states of the L1 dye depend on solvent basicity, highlighting the role of hydrogen bond formation on controlling such states. Density functional theory calculations are performed to gain insight into the photophysical properties of the dye and revealed that H-bonding between the carboxylic groups triggers the dimerization at low concentrations. Using femtosecond transient absorption, we assigned the rate of TICT formation to be in the range (160-650 fs)(-1), depending on the size of the studied cyanoacrylic dye. Therefore, we add herein a new dimension for controlling the formation of the TICT state, in addition to the solvent polarity and acceptor strength parameters. These findings are not limited to the studied dyes, and we expect that numerous organic carboxylic acids dyes show similar properties.
|
|
| 21. |
- El-Zohry, Ahmed M., et al.
(author)
-
Ultrafast Twisting of the Indoline Donor Unit Utilized in Solar Cell Dyes : Experimental and Theoretical Studies
- 2015
-
In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:5, s. 2249-2259
-
Journal article (peer-reviewed)abstract
- Previous time-resolved measurements on D149, the most-studied dye of the indoline family, had shown a fast time-component of 20–40 ps that had tentatively been attributed to structural relaxation. Using femtosecond transient absorption, we have investigated the isolated indoline donor unit (i.e., without acceptor group) and found an ultrafast decay characterized by two lifetimes of 3.5 and 23 ps. Density functional theory calculations show π-bonding and π*-antibonding character of the central ethylene group for the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), respectively. The LUMO is localized on the flexible vinyl-diphenyl region of the donor unit and a twisting process is assumed to occur as a deactivation process for the excited molecule. This is confirmed by multireference second-order perturbation theory (CASSCF/CASPT2) calculations of the lowest-lying excited state, in which it is shown that torsion of the ethylene bond to 96° and pyramidalization to ca. 100° lead to a conical intersection with the ground state. Embedded in a plastic matrix, where double bond rotation is hindered, the decay is slowed down to nanoseconds. We have also investigated the dyes D102, D131, and D149, possessing the same indoline donor unit, by femtosecond transient absorption and found a similar decay component. The ca. 20 ps deactivation channel in D-family dyes is thus attributed to a twisting process of the donor unit. The fluorescence quantum yields of this unit and D149 were measured, and from comparison, the competition of the discovered twisting deactivation channel to the radiative decay of the excited indoline dyes could be confirmed. Blocking this deactivation channel is expected to further increase efficiency for the indoline dyes.
|
|
| 22. |
- Gao, Jiajia, et al.
(author)
-
Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells : An Electrolyte Effect
- 2018
-
In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:31, s. 26241-26247
-
Journal article (peer-reviewed)abstract
- A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.
|
|
| 23. |
- Hussain, Mushraf, et al.
(author)
-
Spin-Orbit Charge-Transfer Intersystem Crossing of Compact Naphthalenediimide-Carbazole Electron-Donor-Acceptor Triads
- 2021
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 125:38, s. 10813-10831
-
Journal article (peer-reviewed)abstract
- Compact electron donor–acceptor triads based on carbazole (Cz) and naphthalenediimide (NDI) were prepared to study the spin–orbit charge-transfer intersystem crossing (SOCT-ISC). By variation of the molecular conformation and electron-donating ability of the carbazole moieties, the electronic coupling between the two units was tuned, and as a result charge-transfer (CT) absorption bands with different magnitudes were observed (ε = 4000–18 000 M–1 cm–1). Interestingly, the triads with NDI attached at the 3-C position or with a phenyl spacer at the N position of the Cz moiety, thermally activated delayed fluorescence (TADF) was observed. Femtosecond transient absorption (fs-TA) spectroscopy indicated fast electron transfer (0.8–1.5 ps) from the Cz to NDI unit, followed by population of the triplet state (150–600 ps). Long-lived triplet states (up to τT = 45–50 μs) were observed for the triads. The solvent-polarity-dependent singlet-oxygen quantum yield (ΦΔ) is 0–26%. Time-resolved electron paramagnetic resonance (TREPR) spectral study of TADF molecules indicated the presence of the 3CT state for NDI-Cz-Ph (zero-field-splitting parameter D = 21 G) and an 3LE state for NDI-Ph-Cz (D = 586 G). The triads were used as triplet photosensitizers in triplet–triplet annihilation upconversion by excitation into the CT absorption band; the upconversion quantum yield was ΦUC = 8.2%, and there was a large anti-Stokes shift of 0.55 eV. Spatially confined photoexcitation is achieved with the upconversion using focusing laser beam excitation, and not the normally used collimated laser beam, i.e., the upconversion was only observed at the focal point of the laser beam. Photo-driven intermolecular electron transfer was demonstrated with reversible formation of the NDI–• radical anion in the presence of the sacrificial electron donor triethanolamine.
|
|
| 24. |
- Zietz, Burkhard, et al.
(author)
-
Photoisomerization of the cyanoacrylic acid acceptor group - a potential problem for organic dyes in solar cells
- 2014
-
In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:6, s. 2251-2255
-
Journal article (peer-reviewed)abstract
- Organic solar cell dyes containing the most common anchoring group, cyanoacrylic acid, are shown to be photolabile and undergo photoisomerization. This may have significant consequences for dye-sensitized solar cells, as isomerisation competes with electron injection and leads to modifications of the dye and surface arrangement.
|
|
