1,721,064 research outputs found
Copper(I) phenanthroline complexes and supramolecular systems containing fullerenes: Photophysics, photochemistry and potential applications in sustainable energy technologies.
No full textChemistry can contribute, in many different ways to solve the challenges we are facing to modify our inefficient and fossil-fuel based energy system. The present work was motivated by the search for efficient photoactive materials to be employed in the context of the energy problem: materials to be utilized in energy efficient devices and in the production of renewable electricity and fuels.
We presented a new class of copper complexes, that could find application in lighting techhnologies, by serving as luminescent materials in LEC, OLED, WOLED devices. These technologies may provide substantial energy savings in the lighting sector. Moreover, recently, copper complexes have been used as light harvesting compounds in dye sensitized photoelectrochemical solar cells, which offer a viable alternative to silicon-based photovoltaic technologies. We presented also a few supramolecular systems containing fullerene, e.g. dendrimers, dyads and triads.The most complex among these arrays, which contain porphyrin moieties, are presented in the final chapter. They undergo photoinduced energy- and electron transfer processes also with long-lived charge separated states, i.e. the fundamental processes to power artificial photosynthetic systems
Artificial photosynthesis: Solar to fuel
No full textArtificial photosynthesis which is an appealing strategy for producing sustainable fuels, and also works efficiently is discussed. Plant photosynthesis demonstrates the viability of directly converting sunlight into chemical fuels, which involves storing the energy from the incident solar irradiation in the form of chemical bonds. Water splitting is one of two basic steps in photosynthesis and the only one of the two that requires light, the other being the conversion of CO2into organic molecules such as sugars. The solar energy is absorbed by the charge-transfer moiety, which subsequently drives multielectron redox reactions at the catalytic centre. The nanoporous silica is also important for its compartmentalized structure and robustness, its high surface area and the possibility to vary the metals in the catalytic centre, giving the chance to explore different catalytic activities
Electron Transfer Dynamics in Dye-Sensitized Solar Cells
No full textIn this review, we address the materials design parameters that control the processes of charge separation, and thereby device efficiency, in dye-sensitized photoelectrochemical solar cells. The review starts with an overview of the structure, energetics and kinetics of dye-sensitized solar cells. It then goes on to consider in more detail the parameters determining the efficiency of the two primary charge separation steps in these devices: electron injection from the dye excited state into the metal oxide electrode, and regeneration of the dye ground state by the redox electrolyte. We consider the kinetic competition between these desired charge separation steps and the undesired loss pathways of excited state decay to ground and electron recombination with dye cations. The review avoids detailed mathematical and spectroscopic discussion, but rather tries to summarize the key conclusions relevant to materials design. A recurring theme of the review is the energy cost of achieving charge separation, and how this limits device performance. A further factor addressed in this review is real as opposed to ideal materials behavior, including, for example, consideration of the implications of empirical observations of an exponential density of acceptor states in the metal oxide, as well as identification of unresolved issues in our current understanding
The Bright Side of Perovskites
No full textIncubating in the rise of perovskite photovoltaic era, the advances in material design encourage further promising optoelectronic exploitations. Here, we evaluate halide perovskite envisioning light-emitting applications, with a particular focus to the role that this material can effectively play in the field, discussing advantages and limitations with respect to state of art competing players. Specific benefits derive from the use of low dimensional and nanostructured perovskites, marginally exploited in photovoltaic devices, allowing for a tuning of the excited states properties and for the obtainment of intrinsic resonating structures. Thanks to these unique properties, halide perovskite ensure a great potential for the development of high-power applications, such as lighting and lasing
Plasma‐Based Technologies for Halide Perovskite Photovoltaics
No full textPlasma-based technologies are at the frontier of material processing for several applications, from packaging to agronomy to photovoltaics. These processes allow for a fine-tuning of material properties by engineering deposition, interaction with the substrate, and final surface characteristics at the atomistic level. As metal halide perovskite (MHP) solar cells enter the path toward commercialization, plasma processing can be seen as a powerful material manipulation tool already settled within industrially relevant procedures. In this perspective, the impact that these methods can have on different aspects of perovskite solar cells technology is envisioned, focusing on the direct interaction between plasma and MHPs. The use of plasma processes is foreseen for the deposition or crystallization of MHPs films, for treating their surface, as well as for the creation of suitable coatings either on top of perovskite layer and/or as encapsulants of the whole solar converting devices
Polymer-based nano-inks for solar cells
No full textPolymer-based nano-inks represent a versatile class of materials exploited in fundamental materials science as in cutting-edge technologies. An intelligent selection of polymer and filler can generate a library of nanocomposites with programmable functionalities. Owing to this exceptional and facile tunability of solid-state physical–chemical properties and broad prospects for applications, polymer-based nano-inks are envisioned as cornerstone constituent of next-generation, low-cost optoelectronic devices.
In the last decade, the surge of hybrid halide perovskite materials represented a fundamental breakthrough in contemporary optoelectronics, particularly in solar cells; therefore, numerous strategies have been explored for incorporating polymer-based nano-inks into halide perovskite-based photovoltaic devices. Polymeric materials have been exploited in different fashions, as to improve the processability, mechanical robustness and moisture tolerance of perovskite materials, and to fabricate more efficient transporting layers or printable electrodes for perovskite solar cells
Tunable photophysical properties of phenyleneethynylene based bipyridine ligands
No full textA bipyridine-based system with phenyleneethynylene at the 4,4' positions (1) and its p-methyl (2) and p-methoxy (3) substituted derivatives were synthesized via Sonogashira coupling reactions. The photophysical properties of 1-3 and their related H+ and Zn2+ adducts (1:H+-3:H+ and 1:Zn2+-3:Zn2+) were investigated, as a function of solvent polarity, by using steady-state and time-resolved spectroscopic techniques. Molecular systems 1-3 exhibit trans conformation, whereas adducts with H+ and Zn2+ are conformationally locked cis species. The unsubstituted compound 1 emits at 360 nm with low fluorescence quantum yield (phi(fl) = 0.2%) regardless of the solvent polarity. Fluorescence spectra of 2 and 3 are bathochromically shifted in polar solvents, and the p-methoxy (3) derivative possesses phi(fl) as high as 12%. Complexation of 1-3 with H+ or Zn2+ in acetonitrile causes red-shift of the lowest energy absorption bands, whereas dramatic changes of the emission properties are found as a function of the electron donating ability of the substituents on the phenyleneethynylene moiety (-CH3 or -OCH3), suggesting a charge-transfer character of the lowest electronic transition of 1-3. 1:H+, 1:Zn2+, 2:H+ and 2:Zn2+ exhibit intense fluorescence with phi(fl) up to 33% (1:Zn2+) whilst 3:H+ and 3:Zn2+ are found to be weakly emissive. The singlet radiative and non-radiative rate constants of compounds and complexes were determined, along with triplet parameters, via phosphorescence and transient absorption spectroscopy. More conclusive evidence regarding the protonation of bipyridine nitrogen atoms of compounds 1-3 were obtained through 1H NMR titration studies. These studies indicate that the conjugate molecular systems based on 2,2'-bipyridine and phenyleneethenylenes possess tunable optical properties which can be further utilized for preparing organic and inorganic luminophores with potential application in optoelectronic systems
Synthesis, Properties, and Modeling of Cs1–xRbxSnBr3 Solid Solution: A New Mixed-Cation Lead-Free All-Inorganic Perovskite System
No full textIn the present work, the substitution of cesium (Cs+) with rubidium (Rb+) in fully inorganic tin bromide perovskites Cs1-xRbxSnBr3, has been experimentally demonstrated by synthesizing pure single-phase samples in the CsSnBr3-Cs0.70Rb0.30SnBr3 compositional range. The substitution of Cs with Rb is responsible for structural modification from cubic to orthorhombic symmetry, which has been correlated with optical properties, as the band gap varies from 1.719 to 1.817 eV from CsSnBr3 to Cs0.70Rb0.30SnBr3 sample. Notably, all of the rubidium-embedding alloys present good air stability. All of these results are very straightforward and open the possibility to exploit the electrical and optical capabilities of this very promising family of lead-free materials
Tunable photophysical properties of phenyleneethynylene based bipyridine ligands
No full textA bipyridine-based system with phenyleneethynylene at the 4,4’ positions (1) and its p-methyl (2) and p-methoxy (3) substituted derivatives were synthesized via Sonogashira coupling reactions. The photophysical properties of 1-3 and their related H+ and Zn2+ adducts (1:H+-3:H+ and 1:Zn2+-3:Zn2+) were investigated, as a function of solvent polarity, by using steady-state and time-resolved spectroscopic techniques. Molecular systems 1-3 exhibit trans conformation, whereas adducts with H+ and Zn2+ are conformationally locked cis species. The unsubstituted compound 1 emits at 360 nm with low fluorescence quantum yield (phi(fl) = 0.2%) regardless of the solvent polarity. Fluorescence spectra of 2 and 3 are bathochromically shifted in polar solvents, and the p-methoxy (3) derivative possesses phi(fl) as high as 12%. Complexation of 1-3 with H+ or Zn2+ in acetonitrile causes red-shift of the lowest energy absorption bands, whereas dramatic changes of the emission properties are found as a function of the electron donating ability of the substituents on the phenyleneethynylene moiety (-CH3 or -OCH3), suggesting a charge-transfer character of the lowest electronic transition of 1-3. 1:H+, 1:Zn2+, 2:H+ and 2:Zn2+ exhibit intense fluorescence with phi(fl) up to 33% (1:Zn2+) whilst 3:H+ and 3:Zn2+ are found to be weakly emissive. The singlet radiative and non-radiative rate constants of compounds and complexes were determined, along with triplet parameters, via phosphorescence and transient absorption spectroscopy. More conclusive evidence regarding the protonation of bipyridine nitrogen atoms of compounds 1-3 were obtained through 1H NMR titration studies. These studies indicate that the conjugate molecular systems based on 2,2’-bipyridine and phenyleneethenylenes possess tunable optical properties which can be further utilized for preparing organic and inorganic luminophores with potential application in optoelectronic systems
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