Search Results (17)

The synthesis of Mn-TiO₂/TiO₂, together with its application as a photoanode for solar flow batteries (SFBs), is reported herein. Both the pure TiO₂ electrode and the Mn-TiO₂/TiO₂ based composite electrode were prepared using the sol–gel spin-coating technique. The incorporation of a Mn-TiO₂ layer led to the enhancement of the built-in electric field within the composite photoanode. This enhancement not only improved the light-harvesting capability of the photoanode but also suppressed the recombination of charge carriers, consequently enhancing the photocatalytic efficiency. Furthermore, the optimal annealing temperature and the optimum TiO₂ loading were systematically controlled and optimized to maximize the photoelectric conversion efficiency of the composite photoanode. Ultimately, the optimized Mn-TiO₂ composite photoanode was integrated into a monolithic solar flow battery. The results demonstrate that the battery’s photocharging current density reaches 300 μA·cm⁻². The photocharging current density was relatively increased by 150%. Full article

We investigate spin-to-charge conversion via the Edelstein effect in a 2D Rashba electron gas using the semiclassical Boltzmann approach. We analyze the magnetization arising from the direct Edelstein effect, taking into account an anisotropic Rashba model. We study how this effect depends on the effective masses and Rashba spin–orbit coupling parameters, extracting analytical expressions for the high electronic density regime. Indeed, it is possible to manipulate the anisotropy introduced into the system through these parameters to achieve a boost in the Edelstein response compared to the isotropic Rashba model. We also discuss the theoretical framework to study the inverse Edelstein effect and calculate self-consistently the electric current induced by the proximity of the system to a ferromagnet. These results provide insights into the role of Rashba spin–orbit coupling and anisotropic effects in spin–charge conversion phenomena. Full article

Carbon fiber is known for being lightweight and adaptable, making it useful for various current and future applications. However, to broaden the use of carbon fibers beyond niche applications, production costs must be lowered. A potential approach to achieving this is by using more affordable raw materials, such as lignin, which is renewable, cost-effective, and widely available compared with the materials commonly used in industry today. This study explores the impact of metal ions on the quality of carbon fiber derived from lignin, focusing on its mechanical and electrochemical properties and morphology. The effect of a specific metal ion (Ni(NO₃)₂·6H₂O) was examined by incorporating it into the spinning solution. The carbonization stage of the fiber was conducted at temperatures of 800, 900, and 1000 °C in an inert atmosphere. Scanning electron microscopy (SEM) analysis showed no defects or damage in any of the fibers. Therefore, it was concluded that moderate concentrations of Ni²⁺ ions in the fibers do not influence the stabilization or carbonization processes, thus leaving the mechanical properties of the final carbon fiber unchanged. These carbon nanofibers were also tested as a sustainable alternative to the non-renewable materials used in electrodes for energy storage and conversion devices, such as supercapacitors. Electrochemical performance was assessed in a 6 M KOH solution using a two-electrode cell configuration. Galvanostatic charge–discharge tests were performed at different current densities (0.1, 0.25, 0.5, 1.0, and 2.0 A g⁻¹). The specific capacitance of the carbon nanofibers was determined from CVA data at various scan rates: 5, 10, 20, 40, 80, and 160 mV s⁻¹. The results indicated that at 0.1 A g⁻¹, the capacitance reached 108 F g⁻¹, and at a scan rate of 5 mV s⁻¹, it was 91 F g⁻¹. The innovation of this work lies in its use of lignin, a renewable and widely available material, to produce carbon fibers, reducing costs compared with traditional methods. Additionally, the incorporation of nickel ions enhances the electrochemical properties of the fibers for supercapacitor applications without compromising their mechanical performance. Full article

In this work, layer-by-layer organic photovoltaics (LbL OPVs) were prepared by sequentially spin-coating PM1 and L8-BO solutions. The solvent additive 1,8-diiodooctane (DIO), which has a high boiling point, and solid additive l,3,5-trichlorobenzene (TCB), which has a high volatile, were deliberately selected to incorporate with the L8-BO solutions. The power conversion efficiency (PCE) of LbL OPVs was considerably enhanced from 17.43% to 18.50% by employing TCB as the additive, profiting by the concurrently increased short-circuit current density (J_SC) of 26.74 mA cm⁻² and a fill factor (FF) of 76.88%. The increased J_SCs of LbL OPVs with TCB as additive were ascribed to the tilted-up absorption edge in the long wavelength range and the external quantum-efficiency spectral difference between LbL OPVs with and without TCB as an additive. The molecular arrangement of L8-BO and the PM1 domain was enhanced with TCB as an additive, which was most likely responsible for the increased charge mobilities in the layered films processed with additives. It was indicated that the dynamic film-forming process of the acceptor layers plays a vital role in achieving efficient LbL OPVs by employing additive strategy. Over 6% PCE improvement of the LbL OPVs with PM1/L8-BO as the active layers can be achieved by employing TCB as additive. Full article

In recent years, renewable and sustainable triboelectric nanogenerators have attracted attention due to their high energy conversion rate, and enhancing their functionality further contributes to their applicability across various fields. A pH-sensitive triboelectric nanogenerator (pH-TENG) has been prepared by electrostatic spinning technology, with anthocyanin as the pH indicator and environmentally friendly polyvinyl alcohol (PVA) as the substrate. Among many friction-negative materials, the pH-TENG exhibits the best combination with fluorinated ethylene propylene (FEP) and yields an open-circuit voltage of 62 V, a short-circuit current of 370 nA, and a transferred charge of 21.8 nC. At a frequency of 3 Hz, it can charge a 4.7 μF capacitor to 2 V within 45 s, effectively powering a thermometer. Furthermore, the presence of anthocyanin does not affect the pH-TENG’s power generation performance and enables the monitoring of a wide range of environmental pH changes, with an ΔE change of 28.8 ± 7.6. Therefore, pH-TENG prepared with environmentally friendly materials can bring new available materials to the biological and medical fields. Full article

Thermoelectric phenomena, such as the Anomalous Nernst and Longitudinal Spin Seebeck Effects, are promising for sensor applications in the area of renewable energy. In the case of flexible electronic materials, the request is even larger because they can be integrated into devices having complex shape surfaces. Here, we reveal that Pt promotes an enhancement of the thermoelectric response in Co-rich ribbon/Pt heterostructures due to the spin-to-charge conversion. Moreover, we demonstrated that the employment of the thermopiles configuration in this system increases the induced thermoelectric current, a fact related to the considerable decrease in the electric resistance of the system. By comparing present findings with the literature, we were able to design a flexible thermopile based on LSSE without the lithography process. Additionally, the thermoelectric voltage found in the studied flexible heterostructures is comparable to the ones verified for rigid systems. Full article

Charge and spin density waves are typical symmetry broken states of quasi one-dimensional electronic systems. They demonstrate such common features of all incommensurate electronic crystals as a spectacular non-linear conduction by means of the collective sliding and susceptibility to the electric field. These phenomena ultimately require for emergence of static and transient topological defects: there are dislocations as space vortices and space-time vortices known as phase slip centers, i.e., a kind of instantons. Dislocations are statically built-in under a transverse electric field; their sweeping provides a conversion among the normal carriers and condensate which ensures the onset of the collective sliding. A special realization in a high magnetic field, when the density wave is driven by the Hall voltage, originated by quantized normal carriers, reveals the dynamic vorticity serving to annihilate compensating normal and collective currents. Spin density waves, with their rich multiplicative order parameter, bring to life complex objects with half-integer topologically bound vorticities in charge and spin degrees of freedom. We present the basic concepts and modelling results of the stationary states and their transient dynamics involving vorticity. The models take into account multiple fields in their mutual non-linear interactions: the complex order parameter, the self-consistent electric field, and the reaction of normal carriers. We explore the traditional time-dependent Ginzburg–Landau approach and introduce its generalization allowing the treatment of intrinsic normal carriers. The main insights and illustrations come from numerical solutions to partial differential equations for the dissipative dynamics of one and two space dimensions. Full article

Due to its high sensitivity and because it does not rely on the magneto-optical response, terahertz (THz) emission spectroscopy has been used as a powerful time-resolved tool for investigating ultrafast demagnetization and spin current dynamics in nanometer-thick ferromagnetic (FM)/heavy metal (HM) heterostructures. Here, by changing the order of the conductive HM coating on the FM nanometer film, the dominant electric dipole contribution to the laser-induced THz radiation can be unraveled from the ultrafast magnetic dipole. Furthermore, to take charge equilibration into account, we separate the femtosecond laser-induced spin-to-charge converted current and the instantaneous discharging current within the illuminated area. The THz emission spectroscopy gives us direct information into the coupled spin and charge dynamics during the first moments of the light–matter interaction. Our results also open up new perspectives to manipulate and optimize the ultrafast charge current for promising high-performance and broadband THz radiation. Full article

One of the most amazing photovoltaic technologies for the future is the organic–inorganic lead halide perovskite solar cell, which exhibits excellent power conversion efficiency (PCE) and can be produced using a straightforward solution technique. Toxic lead in perovskite can be replaced by non-toxic alkaline earth metal cations because they keep the charge balance in the material and some of them match the Goldschmidt rule’s tolerance factor. Therefore, thin films of MAPbI₃, 1% Bi and 0%, 0.5%, 1% and 1.5% Sn co-doped MAPbI₃ were deposited on FTO-glass substrates by sol-gel spin-coating technique. XRD confirmed the co-doping of Bi–Sn in MAPbI₃. The 1% Bi and 1% Sn co-doped film had a large grain size. The optical properties were calculated by UV-Vis spectroscopy. The 1% Bi and 1% Sn co-doped film had small E_g, which make it a good material for perovskite solar cells. These films were made into perovskite solar cells. The pure MAPbI₃ film-based solar cell had a current density (J_sc) of 9.71 MA-cm⁻², its open-circuit voltage (V_oc) was 1.18 V, its fill factor (FF) was 0.609 and its efficiency (η) was 6.98%. All of these parameters were improved by the co-doping of Bi–Sn. The cell made from a co-doped MAPbI₃ film with 1% Bi and 1% Sn had a high efficiency (10.03%). Full article

Polymer photovoltaics (PV) offer the advantage of low-cost, mass-produced, flexible PV films, but they generally suffer from a low-power conversion efficiency (PCE) compared to silicon. This paper studies ITO/PEDOT:PSS/bulk heterojunction/Al PV cells, where two different bulk heterojunction blends are researched: P3HT/PC₆₁BM and PCDTBT/PC₇₀BM. The addition of multiwall carbon nanotubes (CNT) is explored as a conductive network to accelerate the electron transport and extraction to the outer aluminium current collector while reducing the chance of charge recombinations. Several layer deposition techniques are investigated: spin coating and casting, as well as techniques that would induce transverse orientation of polymer grains, including inkjet printing, electrophoresis and the application of a transverse AC field during annealing. Transverse orientation techniques produced architectures that would facilitate charge transport without recombinations, but it is recommended to avoid such techniques for the deposition of conductive PEDOT:PSS and CNT layers as they create a high surface roughness that leads to short circuiting. The best performing PV cell is the ITO/PEDOT:PSS/PCDTBT/PC₇₀BM/CNT/Al structure with a PCE of 11%. Full article

The hole transport layer (HTL) is one of the main factors affecting the efficiency and stability of perovskite solar cells (PSCs). However, obtaining HTLs with the desired properties through current preparation techniques remains a challenge. In the present study, we propose a new method which can be used to achieve a double-layer HTL, by inserting a CuI layer between the perovskite layer and Spiro-OMeTAD layer via a solution spin coating process. The CuI layer deposited on the surface of the perovskite film directly covers the rough perovskite surface, covering the surface defects of the perovskite, while a layer of CuI film avoids the defects caused by Spiro-OMetad pinholes. The double-layer HTLs improve roughness and reduce charge recombination of the Spiro-OMeTAD layer, thereby resulting in superior hole extraction capabilities and faster hole mobility. The CuI/Spiro-OMeTAD double-layer HTLs-based devices were prepared in N₂ gloveboxes and obtained an optimized PCE (photoelectric conversion efficiency) of 17.44%. Furthermore, their stability was improved due to the barrier effect of the inorganic CuI layer on the entry of air and moisture into the perovskite layer. The results demonstrate that another deposited CuI film is a promising method for realizing high-performance and air-stable PSCs. Full article

Spin-to-charge conversion is a central process in the emerging field of spintronics. One of its main applications is the electrical detection of spin currents, and for this, the inverse spin Hall effect (ISHE) has become one of the preferred methods. We studied the thickness dependence of the ISHE in iridium oxide (IrO${}_2$) thin films, producing spin currents by means of the spin Seebeck effect in $\gamma -$Fe${}_2$O${}_3$/IrO${}_2$ bilayers prepared by pulsed laser deposition (PLD). The observed ISHE charge current density, which features a maximum as a consequence of the spin diffusion length scale, follows the typical behaviour of spin-Hall-related phenomena. By fitting to the theory developed by Castel et al., we find that the spin Hall angle ${\theta }_{\mathrm{SH}}$ scales proportionally to the thin film resistivity, ${\theta }_{\mathrm{SH}}\propto {\rho }_{\mathrm{c}}$, and obtains a value for the spin diffusion length ${\lambda }_{\mathrm{IrO}}{}_2$ of ${\lambda }_{\mathrm{IrO}}{}_2=3.3\left(7\right)$ nm. In addition, we observe a negative ${\theta }_{\mathrm{SH}}$ for every studied thickness and temperature, unlike previously reported works, which brings the possibility of tuning the desired functionality of high-resistance spin-Hall-based devices. We attribute this behaviour to the textured growth of the sample in the context of a highly anisotropic value of the spin Hall conductivity in this material. Full article

We report on the fabrication and study of bulk heterojunction (BHJ) solar cells based on a novel combination of a donor–acceptor poly(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N0-diphenyl)-N,N′di(p-butyl-oxy-pheyl)-1,4-diamino-benzene) (PFB) and [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) blend composed of 1:1 by volume. indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate (PEDOT:PSS)/PFB–PCBM/Ag BHJ solar cells are fabricated by a facile cost-effective spin-coating technique. The thickness of the active film (PFB–PCBM) plays an important role in the efficiency of light absorption, exciton creation, and dissociation into free charges that results in higher power conversion efficiency (PCE). In order to optimize the PCE as a function of active layer thickness, a number of solar cells are fabricated with different thicknesses of PFB–PCBM films at 120, 140, 160, 180, and 200 nm, and their photovoltaic characteristics are investigated. It is observed that the device with a 180 nm thick film demonstrates a maximum PCE of 2.9% with a fill factor (FF) of 53% under standard testing conditions (STC) (25 °C, 1.5 AM global, and 100 mW/cm²). The current–voltage (I-V) properties of the ITO/PEDOT:PSS/PFB–PCBM/Ag BHJ devices are also measured in dark conditions to measure and understand different parameters of the heterojunction. Atomic force microscopy (AFM) and ultraviolet-visible (UV-vis) absorption spectroscopy for the PFB–PCBM film of optimal thickness (180 nm) are carried out to understand the effect of surface morphology on the PCE and bandgap of the blend, respectively. The AFM micrographs show a slightly non-uniform and rough surface with an average surface roughness (R_a) of 29.2 nm. The UV-vis measurements of the PFB–PCBM blend exhibit a reduced optical bandgap of ≈2.34 eV as compared to that of pristine PFB (2.88 eV), which results in an improved absorption of light and excitons generation. The obtained results for the ITO/PEDOT:PSS/PFB–PCBM (180 nm)/Ag BHJ device are compared with the ones previously reported for the P3HT–PCBM blend with the same film thickness. It is observed that the PFB–PCBM-based BHJ device has shown two times higher open circuit voltage (V_oc) and, hence, enhanced the efficiency. Full article

3-(2-Octyldodecyl)thieno[3,2-b]thiophen was successfully synthesized as a new π-bridge with a long branched side alkyl chain. Two donor-π-bridge-acceptor type copolymers were designed and synthesized by combining this π-bridge structure, a fluorinated benzothiadiazole acceptor unit, and a thiophene or thienothiophene donor unit, (PT-ODTTBT or PTT-ODTTBT respectively) through Stille polymerization. Inverted OPV devices with a structure of ITO/ZnO/polymer:PC₇₁BM/MoO₃/Ag were fabricated by spin-coating in ambient atmosphere or N₂ within a glovebox to evaluate the photovoltaic performance of the synthesized polymers (effective active area: 0.09 cm²). The PTT-ODTTBT:PC₇₁BM-based structure exhibited the highest organic photovoltaic (OPV) device performance, with a maximum power conversion efficiency (PCE) of 7.05 (6.88 ± 0.12)%, a high short-circuit current (J_sc) of 13.96 mA/cm², and a fill factor (FF) of 66.94 (66.47 ± 0.63)%; whereas the PT-ODTTBT:PC₇₁BM-based device achieved overall lower device performance. According to GIWAXS analysis, both neat and blend films of PTT-ODTTBT exhibited well-organized lamellar stacking, leading to a higher charge carrier mobility than that of PT-ODTTBT. Compared to PT-ODTTBT containing a thiophene donor unit, PTT-ODTTBT containing a thienothiophene donor unit exhibited higher crystallinity, preferential face-on orientation, and a bicontinuous interpenetrating network in the film, which are responsible for the improved OPV performance in terms of high J_sc, FF, and PCE. Full article

The spin galvanic effect (SGE) describes the conversion of a non-equilibrium spin polarization into a charge current and has recently attracted renewed interest due to the large conversion efficiency observed in oxide interfaces. An important factor in the SGE theory is disorder which ensures the stationarity of the conversion. Through this paper, we propose a procedure for the evaluation of the SGE on disordered lattices which can also be readily implemented for multiband systems. We demonstrate the performance of the method for a single-band Rashba model and compare our results with those obtained within the self-consistent Born approximation for a continuum model. Full article