A Density Functional Theory Study of the Physico-Chemical Properties of Alkali Metal Titanate Perovskites for Solar Cell Applications.

The urgent need to shift from non-renewable to renewable energy sources has caused widespread interest in photovoltaic technologies that allow us to harness readily available and sustainable solar energy. In the past decade, polymer solar cells (PSCs) and perovskite solar cells (Per-SCs) have gained attention owing to their low price and easy fabrication process. Charge transport layers (CTLs), transparent conductive electrodes (TCEs), and metallic top electrodes are important constituents of PSCs and Per-SCs, which affect the efficiency and stability of these cells. Owing to the disadvantages of current materials, including instability and high cost, the development of alternative materials has attracted significant attention. Owing to their more flexible physical and chemical characteristics, ternary oxides are considered to be appealing alternatives, where ATiO3 materials-a class of ternary perovskite oxides-have demonstrated considerable potential for applications in solar cells. Here, we have employed calculations based on the density functional theory to study the structural, optoelectronic, and magnetic properties of ATiO3 (A=Li, Na, K, Rb, and Cs) in different crystallographic phases to determine their potential as PSCs and Per-SCs materials. We have also determined thermal and elastic properties to evaluate their mechanical and thermal stability. Our calculations have revealed that KTiO3 and RbTiO3 possess similar electronic properties as half-metallic materials, while LiTiO3 and CsTiO3 are metallic. Semiconductor behavior with a direct band gap of 2.77 eV was observed for NaTiO3, and calculations of the optical and electronic properties predicted that NaTiO3 is the most appropriate candidate to be employed as a charge transfer layer (CTL) and bottom transparent conducting electrode (TCE) in PSCs and Per-SCs, owing to its transparency and large bandgap, whereas NaTiO3 also provided superior elastic and thermal properties. Among the metallic and half-metallic ATiO3 compounds, CsTiO3 and KTiO3 exhibited the most appropriate features for the top electrode and additional absorbent in the active layer, respectively, to enhance the performance and stability of these cells.

Binary solvent-reinforced poly (vinyl alcohol)/sodium alginate double network hydrogel as a highly ion-conducting, resilient, and self-healing gel polymer electrolyte for flexible supercapacitors.

We present a reliable approach for producing high-performance ion-conducting gel polymer electrolytes (GPEs) based on the sodium chloride (NaCl)-integrated dual network hydrogel of poly (vinyl alcohol)/sodium alginate (PVA/SA) using a binary solvent system of ethylene glycol (EG) and water, providing exceptional ionic conductivity, mechanical strength, and self-healing properties. Different GPEs were produced via the freezing-thawing method using different v/v% of EG and water (named PVA/SA/EG). The best PVA/SA/EG GPE provided a maximum ionic conductivity of 25 mS cm-1, astonishing mechanical strength of 0.42 MPa, exceptional stretchability of 462 %, and remarkable self-healing properties. The binary solvent system- and water-based GPEs were utilized in the construction of symmetric supercapacitors (SSCs) using carbon cloth electrodes and their electrochemical performance were compared. At a current density of 0.5 mA cm-2, the SSC prepared using the best PVA/SA/EG GPE demonstrated a high specific capacity of 577.21 mF cm-2, maintained 94.5 % capacitance after 5000 cycles at 1 mA cm-2, and provided an energy density of 80.14 mWh cm-2 while operating at a power density of 293.3 mW cm-2. The flexible SSC prepared based on this GPE demonstrated outstanding flexibility, while no significant decline in capacitive performance and ionic conductivity was detected when it was bent.

In Situ Electrochemical Cobalt Doping in Perovskite-Structured Lanthanum Nickelate Thin Film Toward Energy Conversion Enhancement of Polymer Solar Cells.

This study demonstrates that the electrochemical doping of lanthanum nickelate (LNO) with cobalt ions is a promising strategy for enhancing its physical and electrochemical properties, which are critical for energy storage and conversion devices. LNO emerges as a promising hole transport layer (HTL) in solar cells due to its stability, large band gap, and high transparency. Nevertheless, its low conductivity and improperly aligned band positions are persistent problems. Here, in a pioneering endeavor, Co-doped LNO thin films were synthesized electrochemically and applied as the HTL in polymer solar cells (PSCs). Characterization revealed the impact of Co doping on the electrochemical, structural, morphological, and optical properties of LNO thin films. Depending on the Co doping level, PSCs based on 10 mol % Co-doped LNO outperformed pure LNO, achieving a champion efficiency of 6.11% with enhanced short-circuit current density (12.84 mA cm-2), fill factor (68%), open-circuit voltage (0.70 V), and external quantum efficiency (82.6%). This enhancement resulted from decreased series resistance, refined surface morphology, minimized trap-assisted recombination, enhanced conductivity, increased charge carrier production, favorable energy level alignment, and improved current extraction facilitated by LNC0.10O HTL. Moreover, the unencapsulated PSC-LNC0.10O long-term stability notably improved and retained 86% of its initial PCE after 450 h storage in ambient air, 82% after being continuously heated to 85 °C for 300 h, and 80% after operating at maximum power point for 300 h. These findings offer a straightforward approach to enhancing PSC performance through Co doping of LNO, supported by density functional theory (DFT) calculations that validate the experimental results and confirm the improvement in optical properties and stability of PSCs as an HTL.

Self-extinguished and flexible cation exchange membranes based on modified K-Carrageenan/PVA double network hydrogels for electrochemical applications.

It is highly desired and yet challenging to develop eco-friendly cation exchange membranes with a combination of good mechanical, electrochemical, and biocompatible properties with a rational economic efficiency for given applications. In this study, new biocompatible double network (DN) hydrogels were prepared based on a blend of modified K-Carrageenan (KC) and polyvinyl alcohol (PVA). Acrylic acid (AA)-grafted KC (KC-g-(PAA)) and (AA-co-tertbutyl acrylate (TBA))-grafted KC (KC-g-P(AA-co-TBA)) were synthesized through an in situ free radical copolymerization. The grafted copolymers were blended with PVA and mixed with ZrOCl2/KCl and glutaraldehyde (Glu) as the physical and chemical cross-linkers, respectively to produce KC-g-P(AA)/PVA and KC-g-P(AA-co-TBA)/PVA DN hydrogels. The membranes were prepared by a solution casting method. Various techniques were carried out to compare the structural, thermal, mechanical, flammability, and electrochemical properties of the membranes with those of the cross-linked KC, PVA, and KC/PVA membranes. The KC-g-P(AA-co-TBA)/PVA DN membrane showed more desirable properties as the cation exchange membrane with water uptake of 70.7 %, ion exchange capacity of 0.47 meq H+ /g, the ionic conductivity of 1.99 × 10-2 S/cm2, and elongation at break of 71.8 %. The prepared biopolymer membrane is very cost-effective and self-extinguished with admissible conductivity for electrochemical applications.

Novel mesoporous Co3O4-Sb2O3-SnO2 active material in high-performance capacitive deionization.

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes. However, this technique still requires further development of the electrode materials to tackle the ion removal capacity/rate issues. In the present work, we introduce a novel active carbon (AC)/Co3O4-Sb2O3-SnO2 active material for hybrid electrode capacitive deionization (HECDI) systems. The structure and morphology of the developed electrodes were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET)/Barrett-Joyner-Halenda (BJH) techniques, as well as Fourier-transform infrared (FT-IR) spectroscopy. The electrochemical properties were also investigated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The CDI active materials AC/Co3O4 and AC/Co3O4-Sb2O3-SnO2 showed a high specific capacity of 96 and 124 F g-1 at the scan rate of 10 mV s-1, respectively. In addition, the newly-developed electrode AC/Co3O4-Sb2O3-SnO2 showed high capacity retention of 97.2% after 2000 cycles at 100 mV s-1. Moreover, the electrode displayed excellent CDI performance with an ion removal capacity of 52 mg g-1 at the applied voltage of 1.6 V and in a solution of potable water with initial electrical conductivity of 950 µs cm-1. The electrode displayed a high ion removal rate of 7.1 mg g-1 min-1 with an excellent desalination-regeneration capability while retaining about 99.5% of its ion removal capacity even after 100 CDI cycles.

Surface roughness regulation of reduced-graphene oxide/iodine - Based electrodes and their application in polymer solar cells.

The current work presents an iodine-mediated fine-tuning method for the electrical and electrochemical properties of reduced-graphene oxide (r-GO)/iodine - based electrodes for application in ITO-free polymer solar cells (PSCs). A multi-technique investigation was applied to correlate the morphological features of GO thin films (GO TFs) with iodine adsorption during the reduction process by HI vapor, electrochemical band gap, Fermi potential, charge carrier mobility and charge density of iodine/r-GO based electrodes. The electrical and electrochemical characteristics of iodine/r-GO electrodes changed considerably by alteration of their surface roughness and iodine content. Iodine/r-GO TFs with the lowest surface roughness and the highest iodine content exhibited the highest charge carrier density and Fermi potential. Electrochemical impedance spectroscopy (EIS) and quantum Hall effect (QHE) results confirmed the p-type conductivity of r-GOs/iodine-based electrodes. PSCs were fabricated using r-GO/iodine electrodes as the photo-anode to follow the influences of iodine content and surface roughness on the photovoltaic performance of the cells. PSCs prepared based on r-GO/iodine electrodes possessing the lowest surface roughness and the highest iodine content provided the lowest charge transfer resistance (Rct) and remarkably higher (∼48%) PCE.

Time-resolved mapping of water diffusion coefficients in a working soft actuator device.

Diffusion-weighted imaging was employed to spatially map the distribution of the diffusion coefficient of water, D, in bare, water-soaked, Li(+)-exchanged, cast Nafion and in an ionic polymer-metal composite (IPMC) soft actuator element, prepared from this bare Nafion by impregnation with Pt electrodes. D was evaluated in two orthogonal directions: along one of the long dimensions of the sample (Dx) and through its thickness (Dz). D-maps of the IPMC element were obtained both in the absence of an applied potential and in situ during the application of a 3 V dc potential across the thickness of the sample. In the bare Nafion, D-maps showed uniform values of both Dx and Dz of about 6 x 10 (-10) m(2) s(-1). In the IPMC two effects were observed: (i) D at the electroded surfaces of the IPMC was higher than at the center of the sample; (ii) this difference was much greater in Dz than in Dx . Both effects were explained by the influence of the impregnated Pt electrodes on polymer structure. The D-maps in the electrochemical measurements showed high values of D (up to 8 x 10(-10) m(2) s(-1)) at the cathode and low values (from 1 x 10(-10) m(2) s(-1)) at the anode. This was explained in terms of the effect on the Nafion nanostructure of the forced electro-migration of Li(H2O)x(+) species toward the cathode.

Enhancing the photovoltaic performance of bulk heterojunction polymer solar cells by adding Rhodamine B laser dye as co-sensitizer.

Ternary blend (TB) strategy has been considered as an effective method to enhance the photovoltaic performance of bulk heterojunction (BHJ) polymer solar cells (PSCs). Here, we report on TB-based PSCs containing two donor materials; poly-3-hexylthiophene (P3HT) and Rhodamine B (RhB) laser organic dye, and [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) as an acceptor. The influence of RhB weight percentage and injection volume was extensively studied. To gain insight into the influences of RhB on the photovoltaic performance of PSCs, physicochemical and optical properties of TBs were compared with those of BHJ binary blend as a standard. RhB broadened the light absorption properties of the active layer and played a bridging role between P3HT and PC61BM. The PCE and short-circuit current density (Jsc) of the optimized TB-based PSCs comprising of 0.5 wt% RhB reached 5% and 12.12 mA/cm2, respectively. Compared to BHJ standard cell, the PCE and the generated current was improved by two orders of magnitude due to higher photon harvest of the active layer, cascade energy level structure of TB components and a considerable decrease in the charge carrier recombination. The results suggest that RhB can be considered as an effective material for application in PSCs to attain high photovoltaic performance.

In situ magnetic resonance imaging of electrically-induced water diffusion in a nafion ionic polymer film.

By deploying a functioning electrochemical cell inside a Magnetic Resonance Imaging (MRI) instrument, images of the electrically-induced diffusion of water through a Li+ ion-exchanged Nafion ionic polymer film in the form of two-dimensional maps of proton density and transverse relaxation time, T2, were generated and changes in these images over time and with respect to changes made to the applied potential were followed.

Electromechanical behaviour of Nafion-based soft actuators.

Soft actuators based on Ionic Polymer-Metal Composites (IPMCs) are of considerable interest for applications in biomedical devices and robotics. In this work, thin commercial and thick laboratory-prepared Nafion membranes were made into model IPMC actuator devices by incorporation of Pt electrode layers. In extensive electromechanical tests the maximum average tip displacement and maximum force generated were recorded. The effect of amplitude and frequency of the applied voltage on both displacement and force was examined as were the effects of the origin of the Nafion membrane, the Pt loading, the structure of the electrode and the presence or absence of an Au overlayer. The cast samples generated much smaller displacements but much larger forces than the commercial Nafion samples. For all samples, displacement and force increased with increasing applied voltage, with increased number of Pt plating cycles and when an Au overlayer was present but decreased with increasing applied voltage frequency. Waveform analysis of applied voltage, current and force was performed by considering the capacitive nature of the IPMC actuators.

Novel sulfate ion-selective polymeric membrane electrode based on a derivative of pyrilium perchlorate.

A sulfate ion-selective PVC membrane sensor based on 4-(4-bromophenyl)-2,6-diphenylpyrilium perchlorate (BDPP) as a novel sensing material is successfully developed. The electrode shows a good selectivity for sulfate ion with respect to common organic and inorganic anions. The sensor exhibits a good linear response with slope of -28.9+/-0.5 mV per decade over the concentration range of 1.0x10(-6)-1.0x10(-2) M, and a detection limit of 8.0x10(-7) M of SO(4)(2-) ions. The electrode response is independent of pH in the range of 4.0-9.0. The proposed sensor was applied as an indicator electrode in potentiometric titration of sulfate and barium ions, and to the determination of zinc in zinc sulfate tablets.