Nanograss-Assembled NiCo2S4 as an Efficient Platinum-Free Counter Electrode for Dye-Sensitized Solar Cell

Dye-sensitized solar cells (DSSCs) are often viewed as the potential future of photovoltaic systems and have garnered significant attention in solar energy research. In this groundbreaking research, we introduced a novel solvothermal method to fabricate a unique "grass-like" pattern on fluorine-doped tin oxide glass (FTO), specifically designed for use as a counter electrode in dye-sensitized solar cell (DSSC) assemblies. Through rigorous structural and morphological evaluations, we ascertained the successful deposition of nickel cobalt sulfide (NCS) on the FTO surface, exhibiting the desired grass-like morphology. Electrocatalytic performance assessment of the developed NCS-1 showed results that intriguingly rivaled those of the acclaimed platinum catalyst, especially during the conversion of I3 to I- as observed through cyclic voltammetry. Remarkably, when integrated into a solar cell assembly, both NCS-1 and NCS-2 electrodes exhibited encouraging power conversion efficiencies of 6.60% and 6.29%, respectively. These results become particularly noteworthy when compared to the 7.19% efficiency of a conventional Pt-based electrode under similar testing conditions. Central to the performance of the NCS-1 and NCS-2 electrodes is their unique thin and sharp grass-like morphology. This structure, vividly showcased through scanning electron microscopy, provides a vast surface area and an abundance of catalytic sites, pivotal for the catalytic reactions involving the electrolytes in DSSCs. In summation, given their innovative synthesis approach, affordability, and remarkable electrocatalytic attributes, the newly developed NCS counter electrodes stand out as potent contenders in future dye-sensitized solar cell applications.

Triplet-triplet annihilation mediated photon upconversion solar energy systems

Solar energy harvesting is among the best solutions for a global transition toward carbon-neutral energy technologies. The existing solar energy harvesting technologies like photovoltaics (PV) and emerging molecular concepts such as solar fuels and molecular solar thermal energy storage (MOST) are rapidly developing. However, to realize their full potential, fundamental solar energy loss channels like photon transmission, recombination, and thermalization need to be addressed. Triplet-triplet annihilation mediated photon upconversion (TTA-UC) is emerging as a way to overcome losses due to the transmission of photons below the PV/chromophore band gap. However, there are several challenges related to the integration of efficient solid-state TTA-UC systems into efficient devices such as: wide band absorption, materials sustainability, and device architecture. In this article, we review existing work, identify and discuss challenges as well as present our perspective toward possible future directions.

Ionic liquid dispersed highly conducting polymer electrolyte for supercapacitor application: Current scenario and prospects “ICSEM 2021”

Ionic liquid (IL) is now being considered as a novel contender in the development of highly conducting polymer electrolytes rather than a solvent. It has a significant impact on the electrochemical performance of polymer electrolytes. This study emphasizes the significance of low viscosity IL dispersion within a polymer (PVA) matrix. The electrical, structural and photoelectrochemical properties of the IL-doped polymer electrolyte are discussed in detail. These highly conducting IL doped solid polymer electrolytes show promise towards the development of highly efficient Supercapacitors.

Detailed characterization of the solution kinetics and thermodynamics of biotin, biocytin and HABA binding to avidin and streptavidin

The high affinity (K_D ~ 10⁻¹⁵ M) of biotin for avidin and streptavidin is the essential component in a multitude of bioassays with many experiments using biotin modifications to invoke coupling. Equilibration times suggested for these assays assume that the association rate constant (k_on) is approximately diffusion limited (10⁹ M^-1s^-1) but recent single molecule and surface binding studies indicate that they are slower than expected (10⁵ to 10⁷ M^-1s^-1). In this study, we asked whether these reactions in solution are diffusion controlled, which reaction model and thermodynamic cycle describes the complex formation, and if there are any functional differences between avidin and streptavidin. We have studied the biotin association by two stopped-flow methodologies using labeled and unlabeled probes: I) fluorescent probes attached to biotin and biocytin; and II) unlabeled biotin and HABA, 2-(4’-hydroxyazobenzene)-benzoic acid. Both native avidin and streptavidin are homo-tetrameric and the association data show no cooperativity between the binding sites. The k_on values of streptavidin are faster than avidin but slower than expected for a diffusion limited reaction in both complexes. Moreover, the Arrhenius plots of the k_on values revealed strong temperature dependence with large activation energies (6–15 kcal/mol) that do not correspond to a diffusion limited process (3–4 kcal/mol). Accordingly, we propose a simple reaction model with a single transition state for non-immobilized reactants whose forward thermodynamic parameters complete the thermodynamic cycle, in agreement with previously reported studies. Our new understanding and description of the kinetics, thermodynamics, and spectroscopic parameters for these complexes will help to improve purification efficiencies, molecule detection, and drug screening assays or find new applications.

Quantum efficiency of the photo-induced electronic transfer in dye-TiO2 complexes

We present a method based on a time-dependent self-consistent density functional tight-binding (TD-DFTB) approach, able to predict the quantum efficiency of the photoinjection process in a dye-TiO₂ complex from a fully atomistic picture. We studied the process of charge transfer of three systems with different dyes: catechol (CAT), alizarin (ALZ) and FSD101. Each system was excited with lasers of different energies in the range of 300-2500 nm, studying the efficiency of the induced charge transfer process at the incident energies. We show that the perturbation can produce either hole transfer or electron transfer from the dye to the nanoparticle, therefore affecting the efficiency of the charge transfer in the solar cell when illuminated by broadband radiation.

In situ synthesis, enhanced luminescence and application in dye sensitized solar cells of Y2O3/Y2O2S:Eu3+ nanocomposites by reduction of Y2O3:Eu3

Y₂O₃/Y₂O₂S:Eu³⁺ nanocomposites were successfully prepared by reducing Y₂O₃:Eu³⁺ nanocrystals. The obtained Y₂O₃/Y₂O₂S:Eu³⁺ nanocomposites not only can emit enhanced red luminescence excited at 338 nm, but also can be used to improve the efficiency of the dye sensitized solar cells, resulting an efficiency of 8.38%, which is a noticeable enhancement of 12% compared to the cell without Y₂O₃/Y₂O₂S:Eu³⁺ nanocomposites. The results of the incident photon to current, dynamic light scattering, and diffuse reflectance spectra indicated that the enhancement of the cell efficiency was mainly related to the light scattering effect of Y₂O₃/Y₂O₂S:Eu³⁺ nanocomposites. As a phosphor powder, the emission at ~615 nm of Y₂O₃/Y₂O₂S:Eu³⁺ was split into two sub-bands. Compared with Y₂O₃:Eu³⁺, the ⁵D₀ → ⁷F₀ and ⁵D₀ → ⁷F₁ emissions of Y₂O₃/Y₂O₂S:Eu³⁺ showed a little red-shift.

Enhancement of photocatalytic hydrogen formation under visible illumination by integrating plasmonic Au nanoparticles with a strongly catalytic Ni3S2/carbon nanotube composite

Photocatalytic production of H₂ by water splitting gives a promising solution to growing demands for clean and sustainable energy.

Highly-efficient dye-sensitized solar cells with collaborative sensitization by silyl-anchor and carboxy-anchor dyes

In dye-sensitized solar cells co-photosensitized with an alkoxysilyl-anchor dye ADEKA-1 and a carboxy-anchor organic dye LEG4, LEG4 was revealed to work collaboratively by enhancing the electron injection from the light-excited dyes to the TiO2 electrodes, and the cells exhibited a high conversion efficiency of over 14% under one sun illumination.

Relationship between diffusion of Co3+/Co2+ redox species in nanopores of porous titania stained with dye molecules, dye molecular structures, and photovoltaic performances

Diffusion of Co²⁺ and Co³⁺ in nanopores of porous titania stained with dyes were evaluated. V_oc was obtained for the DSSC with fast Co³⁺ diffusion in nanopores. After staining with long alkyl groups, the efficiency increased from 2.8% to 5.3%.

Effect of donor (tetradecyloxy) and acceptor (carboxamide) groups in trans-stilbene for DSSCs: quantum chemical investigations

Incorporation of tetradecyloxy and carboxamide groups in trans-stilbene molecule (dye) has been investigated first time for Dye Sensitized Solar Cells (DSSCs) applications. To understand the changes in electronic structure, geometry, dipole moment and polarizability of the mentioned dye architecture has been carried out by using density functional theory (DFT) and time dependent DFT calculations using hybrid functional B3LYP method. Further, the semiconductor TiO2 is also used as a model to evaluate the photo conversion efficiency of the chosen dye architecture. Results reveal that tetradecyloxy and carboxamide groups act as an excellent donor and acceptor groups respectively which give rise to larger difference in excited state dipole moment than the ground state. This kind of stilbene based metal free organic dyes are act as a promising sensitizer for practical DSSCs applications.

Rapid dye adsorption via surface modification of TiO2 photoanodes for dye-sensitized solar cells

A facile method for increasing the reaction rate of dye adsorption, which is the most time-consuming step in the production of dye-sensitized solar cells (DSSCs), was developed. Treatment of a TiO2 photoanode with aqueous nitric acid solution (pH 1) remarkably reduced the reaction time required to anchor a carboxylate anion of the dye onto the TiO2 nanoparticle surface. After optimization of the reaction conditions, the dye adsorption process became 18 times faster than that of the conventional adsorption method. We studied the influence of the nitric acid treatment on the properties of TiO2 nanostructures, binding modes of the dye, and adsorption kinetics, and found that the reaction rate improved via the synergistic effects of the following: (1) electrostatic attraction between the positively charged TiO2 surface and ruthenium anion increases the collision frequency between the adsorbent and the anchoring group of the dye; (2) the weak anchoring affinity of NO3(-) in nitric acid with metal oxides enables the rapid coordination of an anionic dye with the metal oxide; and (3) sufficient acidity of the nitric acid solution effectively increases the positive charge density on the TiO2 surface without degrading or transforming the TiO2 nanostructure. These results demonstrate the developed method is effective for reducing the overall fabrication time without sacrificing the performance and long-term stability of DSSCs.

Molecular design principle of all-organic dyes for dye-sensitized solar cells

All-organic dyes have shown promising potential as an effective sensitizer in dye-sensitized solar cells (DSSCs). The design concept of all-organic dyes to improve light-to-electric-energy conversion is discussed based on the absorption, electron injection, dye regeneration, and recombination. How the electron-donor-acceptor-type framework can provide better light harvesting through bandgap-tuning and why proper arrangement of acceptor/anchoring groups within a conjugated dye frame is important in suppressing improper charge recombination in DSSCs are discussed. Separating the electron acceptor from the anchoring unit in the donor-acceptor-type organic dye would be a promising strategy to reduce recombination and improve photocurrent generation.

Covalent Linking Greatly Enhances Photoinduced Electron Transfer in Fullerene-Quantum Dot Nanocomposites: Time-Domain Ab Initio Study

Nonadiabatic molecular dynamics combined with time-domain density functional theory are used to study electron transfer (ET) from a CdSe quantum dot (QD) to the C60 fullerene, occurring in several types of hybrid organic/inorganic nanocomposites. By unveiling the time dependence of the ET process, we show that covalent bonding between the QD and C60 is particularly important to ensure ultrafast transmission of the excited electron from the QD photon-harvester to the C60 electron acceptor. Despite the close proximity of the donor and acceptor species provided by direct van der Waals contact, it leads to a notably weaker QD-C60 interaction than a lengthy molecular bridge. We show that the ET rate in a nonbonded mixture of QDs and C60 can be enhanced by doping. The photoinduced ET is promoted primarily by mid- and low-frequency vibrations. The study establishes the basic design principles for enhancing photoinduced charge separation in nanoscale light harvesting materials.

CuInS2 quantum dot-sensitized TiO2 nanorod array photoelectrodes: synthesis and performance optimization

CuInS2 quantum dots (QDs) were deposited onto TiO2 nanorod arrays for different cycles by using successive ionic layer adsorption and reaction (SILAR) method. The effect of SILAR cycles on the light absorption and photoelectrochemical properties of the sensitized photoelectrodes was studied. With optimization of CuInS2 SILAR cycles and introduction of In2S3 buffer layer, quantum dot-sensitized solar cells assembled with 3-μm thick TiO2 nanorod film exhibited a short-circuit current density (Isc) of 4.51 mA cm-2, an open-circuit voltage (Voc) of 0.56 V, a fill factor (FF) of 0.41, and a power conversion efficiency (η) of 1.06%, respectively. This study indicates that SILAR process is a very promising strategy for preparing directly anchored semiconductor QDs on TiO2 nanorod surface in a straightforward but controllable way without any complicated fabrication procedures and introduction of a linker molecule.