- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Charge transfer processes and carrier dynamics at the pentacene - C60 interface
摘要： Heterostructures of pentacene (PEN) and Buckminsterfullerene (C60) are frequently attracting scientific interest as a well-defined small-molecule model-system for the study of internal interfaces between two organic semiconductors. They are prototypical representatives forming a donor-acceptor combination for studies of fundamental optoelectronic processes in organic photovoltaics. Despite their importance in exciton dissociation, the energetics of their interfacial charge-transfer (CT) states and their microscopic excitation dynamics are not yet clarified and still being discussed. Here, we present steady-state and time-resolved photoluminescence measurements on stacked heterostructures between these two materials. All experiments are performed in the visible and near-infrared spectral regions as CT states are expected at energies below the fundamental electronic transitions of the respective bulk materials. A characteristic, interface specific emission at around 1.13-1.17 eV is found, which we attribute to an interfacial CT state. Its excitation-energy dependence reveals the intricate relaxation dynamics of excitons formed in both constituent materials. Moreover, the analysis of the dynamics of the C60 excitons shows that the lifetime of this state is reduced in the presence of an interface with PEN. This quenching is attributed to a long-range interaction, i.e., the relaxation of excitations into the interfacial CT state.
关键词： organic heterostructures,charge-transfer exciton,light harvesting,donor-acceptor pair,Organic thin films,pentacene,fullerene
更新于2025-09-23 15:22:29
-
Photonic Titanium dioxide film obtained from hard template with chiral nematic structure for environmental application
摘要： In the present work, mesoporous TiO2 with a photonic structure was elaborated using cellulose nanocrystals (CNCs) as a biotemplate by two-step hard template methods. This strategy enables to replicate the chiral nematic (CN) structure of the photonic films (biotemplate) in TiO2 films. A series of iridescent CNCs films with different weight ratios of silica/CNCs composite photonic films were prepared via evaporation induced self-assembly (EISA) method. The films showed iridescent color and tuneable Bragg reflection wavelengths by solely changing the ratio between the silica and the CNCs biotemplate. Polarized optical microscopy (POM) performed on hydride SiO2/CNCs films showed a birefringence and typical fingerprint of chiral nematic structure. This birefringence was also observed for TiO2 films obtained using SiO2 films as a hard template, which suggested the transfer of the chiral nematic structure in TiO2 materials. Afterwards, their optical, morphological and electronic properties were studied by scanning electron microscope (SEM), POM, energy-dispersive X-ray spectroscope (EDX) and time resolved microwave conductivity (TRMC). The photocatalytic activities were evaluated by following the phenol degradation using high performance liquid chromatography (HPLC). The results showed that the structuration of the TiO2 film using a chiral nematic SiO2 film as hard template enhances the photocatalytic performance compared to non-structured mesoporous TiO2.
关键词： hard template,cellulose nanocrystals,iridescent film,evaporation induced self-assembly,light harvesting,phenol degradation,chiral nematic structure
更新于2025-09-23 15:22:29
-
Multicolor Luminescent Patterning via Photoregulation of Electron and Energy Transfer Processes in Quantum Dots
摘要： Ability to create high-contrast multicolor luminescent patterns is essential to realize the full potential of quantum dots (QDs) in display technologies. The idea of using a non-emissive state is adopted in the present work to enhance the color-contrast of QD based photopatterns. This is achieved at a multicolor level by the photoregulation of electron and energy transfer processes in a single QD nanohybrid film, comprising of one QD donor and two dye acceptors. The dominance of photoinduced electron transfer over energy transfer process generates a non-luminescent QD nanohybrid film, which provides the black-background for multicolor patterning. The superior photostability of QDs over dyes is used for the photoregulation of electron and energy transfer processes. Selective photodegradation of electron acceptor dye triggered the onset of energy transfer process, thereby imparting a luminescent color to QD nanohybrid film. Further, a controlled photoregulation of energy transfer process paved the way for multicolor patterning.
关键词： Energy and electron transfer,Thin films,Quantum dots,Multicolor photopatterning,Light harvesting
更新于2025-09-23 15:21:01
-
Minimizing Defect States in Lead Halide Perovskite Solar Cell Materials
摘要： In order to reach the theoretical e?ciency limits of lead-based metal halide perovskite solar cells, the voltage should be enhanced because it su?ers from non-radiative recombination. Perovskite materials contain intrinsic defects that can act as Shockley–Read–Hall recombination centers. Several experimental and computational studies have characterized such defect states within the band gap. We give a systematic overview of compositional engineering by distinguishing the di?erent defect-reducing mechanisms. Doping e?ects are divided into in?uences on: (1) crystallization; (2) lattice properties. Incorporation of dopant in?uences the lattice properties by: (a) lattice strain relaxation; (b) chemical bonding enhancement; (c) band gap tuning. The intrinsic lattice strain in undoped perovskite was shown to induce vacancy formation. The incorporation of smaller ions, such as Cl, F and Cd, increases the energy for vacancy formation. Zn doping is reported to induce strain relaxation but also to enhance the chemical bonding. The combination of computational studies using (DFT) calculations quantifying and qualifying the defect-reducing propensities of di?erent dopants with experimental studies is essential for a deeper understanding and unraveling insights, such as the dynamics of iodine vacancies and the photochemistry of the iodine interstitials, and can eventually lead to a more rational approach in the search for optimal photovoltaic materials.
关键词： semiconductor,solar energy,photovoltaics,doping,thin ?lm materials,voltage loss,stabilization,optimization,charge generation,light harvesting
更新于2025-09-23 15:21:01
-
Heterojunction Incorporating Perovskite and Microporous Metala??Organic Framework Nanocrystals for Efficient and Stable Solar Cells
摘要： In this paper, we present a facile approach to enhance the efficiency and stability of perovskite solar cells (PSCs) by incorporating perovskite with microporous indium-based metal–organic framework [In12O(OH)16(H2O)5(btc)6]n (In-BTC) nanocrystals and forming heterojunction light-harvesting layer. The interconnected micropores and terminal oxygen sites of In-BTC allow the preferential crystallization of perovskite inside the regular cavities, endowing the derived films with improved morphology/crystallinity and reduced grain boundaries/defects. Consequently, the In-BTC-modified PSC yields enhanced fill factor of 0.79 and power conversion efficiency (PCE) of 20.87%, surpassing the pristine device (0.76 and 19.52%, respectively). More importantly, over 80% of the original PCE is retained after 12 days of exposure to ambient environment (25 °C and relative humidity of ~ 65%) without encapsulation, while only about 35% is left to the pristine device.
关键词： Light-harvesting layer,Metal–organic framework,Heterojunction,Perovskite solar cell,Nanocrystal
更新于2025-09-23 15:21:01
-
Robust and Fragile Quantum Effects in the Transfer Kinetics of Delocalized Excitons between B850 Units of LH2 Complexes
摘要： Aggregates of light harvesting 2 (LH2) complexes form the major exciton-relaying domain in the photosynthetic unit of purple bacteria. Application of a generalized master equation to pairs of the B850 units of LH2 complexes, where excitons predominantly reside, provides quantitative information on how the inter-LH2 exciton transfer depends on the distance, relative rotational angle, and the relative energies of the two LH2s. The distance dependence demonstrates significant enhancement of the rate due to quantum delocalization of excitons, the qualitative nature of which remains robust against the disorder. The angle dependence reflects isotropic nature of exciton transfer, which remains similar for the ensemble of disorder. The variation of the rate on relative excitation energies of LH2 exhibits resonance peaks, which, however, is fragile as the disorder becomes significant. Overall, the average transfer times between two LH2s are estimated to be in the range of 4?25 ps for physically plausible inter-LH2 distances.
关键词： light harvesting 2 (LH2) complexes,quantum delocalization,exciton transfer,photosynthetic unit,purple bacteria,disorder
更新于2025-09-23 15:21:01
-
Significant enhancement of light-harvesting efficiency through the formation of [2]pseudorotaxane with γ-cyclodextrin based on a bolaamphiphile of salicylaldehyde azine moiety
摘要： In this work, we have designed and synthesized a bolaamphiphile of salicylaldehyde azine (BSA), which can form [2]pseudorotaxane with γ-cyclodextrin (BSA@γ-CD) in aqueous solution and exhibit remarkable enhancement of the fluorescence emission. Both BSA and BSA@γ-CD assembly can spontaneously form spherical aggregates in aqueous solution with diameter at about 30 nm and 20 nm, respectively. By using BSA and BSA@γ-CD as energy donor and sulforhodamine 101 (SR101) as energy acceptor, we fabricated two artificial light-harvesting systems in aqueous solution. Significantly, an efficient energy transfer process was revealed to occur between the BSA or BSA@γ-CD assembly and the loaded SR101 to obtain high energy transfer efficiency and antenna effect. More importantly, energy transfer efficiency and antenna effect can be greatly improved in these two systems only just by addition of γ-CD.
关键词： Energy transfer,Fluorescence enhancement,Pseudorotaxane,Light-harvesting,Self-assembly
更新于2025-09-23 15:21:01
-
A Biomimetic-Computational Approach to Optimizing the Quantum Efficiency of Photovoltaics
摘要： The most advanced low-cost organic photovoltaic cells have a quantum efficiency of ~10%. This is in stark contrast to plant/bacterial light-harvesting systems which offer quantum efficiencies close to unity. Of particular interest is the highly effective quantum coherence-enabled energy transfer. Noting that quantum coherence is promoted by charged residues and local dielectrics, classical atomistic simulations and Time-Dependent Density Functional Theory (TD-DFT) can be used to identify charge/dielectric patterns and electronic coupling at exactly defined energy transfer interfaces incorporating structural information obtained on photosynthetic protein-pigment complexes. To this end, the project focuses on the first protein-pigment-redox carrier complex of the linear electron transport phosphorylation chain termed photosystem II [PSII]. PSII contains more than 10 major polypeptides in addition to hundreds of pigment molecules amounting to a molecular mass in excess of 1 Mio Dalton. Owing to the complexity and fragility of PSII, this project bases the overall architecture of PSII on in situ EM data providing structural clues about the entire, unperturbed PSII complex. Albeit not to high resolution when compared to X-ray crystallography and NMR spectroscopy, the EM tomographic results and projection maps provide an accurate delineation of the native complex suitable for fitting high-resolution X-ray data of PSII subcomplexes towards an atomistic model of the entire PSII complex. This must also include the light-harvesting antennae, i.e. the light-harvesting chlorophyll (Chl) a/b protein complex [LHCII]. With respect to LHCII one should take into account positioning LHCII next to PSII as well as in a separate, complementary membrane thus permitting to test for both, horizontal (intramembrane) and vertical (intermembrane) energy transfer, respectively. The presence of LHCII in a membrane different from PSII is supported by strong biochemical evidence and tomographic data, and it has also been noted that the organization of LHCII may change in response to environmental conditions.
关键词： photosystem II,biomimetic,computational approach,quantum efficiency,light-harvesting chlorophyll,photovoltaics
更新于2025-09-23 15:19:57
-
Thioalkyl-Functionalized Bithiophene (SBT)-Based Organic Sensitizers for High-Performance Dye-Sensitized Solar Cells
摘要： A series of 3,3′-dithioalkyl-2,2′-bithiophene (SBT)-based organic chromophores were designed and developed for the use in dye-sensitized solar cells (DSSCs). By appropriate structural modification of the SBT π-linkers with different alkyl chains and conjugated thiophene units, chromophore aggregation and interfacial charge recombination could be suppressed to a remarkable degree. Single-crystal and optical/electrochemical data clearly show that the SBT core is nearly planar with the torsional angle <1°, likely via S(alkyl)···S(thiophene) intramolecular locks. Therefore, this highly π-conjugated unit should enhance panchromatic light-harvesting and prove to be an excellent core for organic dye. For comparison, the 3,3′-dialkyl-2,2′-bithiophene (BT)-based dye was also prepared. Under 1 sun (100 mW cm?2) illumination, an optimized SBT-6 dye-sensitized cell indicates a short-circuit current density (JSC) of 17.21 mA cm?2, an open-circuit voltage (VOC) of 0.78 V, and a fill factor (FF) of 0.71, corresponding to a power conversion efficiency (η) of 9.47%, which is nearly two times higher than that of alkylated bithiophene (BT)-based chromophores. Finally, the proposed sensitizer SBT-6 exhibited an excellent η of 23.57% under the T5 fluorescent illumination of 6000 lux. To the best of our knowledge, this is the highest power conversion efficiencies (PCE) value reported to date among the studied thiophene or bithiophene-based chromophores.
关键词： aggregation,T5 fluorescent illumination,panchromatic light-harvesting,3, 3′-dithioalkyl-2, 2′-bithiophene,S(alkyl)···S(thiophene) intramolecular locks
更新于2025-09-23 15:19:57
-
Phenanthrenea??Fuseda??Quinoxaline as Key Building Block for Highly Efficient and Stable Sensitizers in Copper Electrolyte Based Dyea??Sensitized Solar Cells
摘要： Dye-sensitized solar cells (DSSCs) based on Cu(II/I) bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open-circuit voltages (VOC, > 1 V). However, their short-circuit photocurrent density (JSC) has remained modest. The challenge for increasing the JSC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO2 film and fast regeneration by the Cu(I) complex. Here, we report two new D-A-π-A featured sensitizers coded HY63 and HY64, which employ either benzothiadiazole (BT) or phenanthrene-fused-quinoxaline (PFQ) as the auxiliary electron-withdrawing acceptor moiety. In spite of very similar energy levels and absorption onsets, HY64-based DSSCs outperform largely their HY63 counterpart, achieving an outstanding power conversion efficiency (PCE) of 12.5% with superior stability. In depth studies of interfacial charge carrier dynamics show that PFQ is superior to BT in retarding charge recombination resulting in near quantitative collection of photogenerated charge carriers.
关键词： sensitizers,light-harvesting,dye-sensitized solar cells,copper redox shuttle,charge recombination
更新于2025-09-23 15:19:57