Suppressing the Shuttle Effect via Polypyrrole-Coated Te Nanotubes for Advanced Na-Te Batteries.

There is a growing demand for research and development of advanced energy storage devices with high energy density utilizing earth-abundant metal anodes such as sodium metal. Tellurium, a member of the chalcogen group, stands out as a promising cathode material due to its remarkable volumetric capacity, comparable to sulfur, and significantly high electrical conductivity. However, critical issues arise from soluble sodium polytellurides, leading to the shuttle effect. This phenomenon can result in the loss of active materials, self-discharge, and anode instability. Here, we introduce polypyrrole-coated tellurium nanotubes as the cathode materials, where polypyrrole plays a crucial role in preventing the dissolution of polytellurides, as confirmed through operando optical microscopy. The polypyrrole-coated tellurium nanotubes exhibited an outstanding rate performance and long cycle stability in sodium-tellurium batteries. These research findings are anticipated to bolster the viability of polypyrrole-coated tellurium nanotubes as promising cathode materials, making a substantial contribution to the commercialization of sodium-ion battery technology.

Process analysis of microplastic aging during the photochemical oxidation process and its effect on the adsorption behavior of dissolved organic matter.

Information on microplastics (MPs) interactions with dissolved organic matter (DOM) is essential for understanding their environmental impacts. However, research is scarce regarding the adsorption behavior of DOM with different characteristics onto pristine and aged MPs. This research thus investigates MPs aging behavior accelerated by UV/Persulfate and UV/chlorine oxidation processes and the adsorption behavior of organic matter with low-specific ultraviolet absorbance (L-SUVA) and high-SUVA (H-SUVA) characteristics. MPs were degraded by UV/Cl and UV/Persulfate for 30 days. Changes in thermal properties, surface morphology, and chemistry were studied using different analytical techniques. The adsorption behavior was assessed by adsorption kinetic and isotherm study. After oxidation, the surface of the MPs showed a significant increase in the oxygen-containing functional groups, contact angle, surface roughness, and surface energy, and a decrease in crystallinity. The oxidation effect follows the order of UV/Cl > UV/Persulfate. The kinetic and equilibrium data of H-SUVA adsorption on pristine and aged MPs well-fitted the pseudo-second-order and Langmuir model. In contrast, L-SUVA well-fitted the pseudo-first-order and Freundlich model. The adsorption capacity (qm) increased in the following orders: 8.11 > 5.87>4.29 mg g-1 for H-SUVA and 19.81 > 6.662>5.315 mg g-1 for L-SUVA by MPs aged with UV/Cl, UV/Persulfate and pristine MPs, respectively. The larger the surface damage of MPs, the greater the adsorption affinity of DOM. The result was attributed to the physical adsorption process, hydrophobic interactions, electrostatic, hydrogen, and halogen bonding. These findings are beneficial to provide new insights involving the adsorption behavior and interaction mechanisms of DOM onto MPs for the environmental risk assessment.

PbS Quantum Dots-Decorated BiVO4 Photoanodes for Highly Efficient Photoelectrochemical Hydrogen Production.

While metal oxides such as TiO2, Fe2O3, WO3, and BiVO4 have been previously studied for their potential as photoanodes in photoelectrochemical (PEC) hydrogen production, their relatively wide band-gap limits their photocurrent, making them unsuitable for the efficient utilization of incident visible light. To overcome this limitation, we propose a new approach for highly efficient PEC hydrogen production based on a novel photoanode composed of BiVO4/PbS quantum dots (QDs). Crystallized monoclinic BiVO4 films were prepared via a typical electrodeposition process, followed by the deposition of PbS QDs using a successive ionic layer adsorption and reaction (SILAR) method to form a p-n heterojunction. This is the first time that narrow band-gap QDs were applied to sensitize a BiVO4 photoelectrode. The PbS QDs were uniformly coated on the surface of nanoporous BiVO4, and their optical band-gap was reduced by increasing the number of SILAR cycles. However, this did not affect the crystal structure and optical properties of the BiVO4. By decorating the surface of BiVO4 with PbS QDs, the photocurrent was increased from 2.92 to 4.88 mA/cm2 (at 1.23 VRHE) for PEC hydrogen production, resulting from the enhanced light-harvesting capability arising from the narrow band-gap of the PbS QDs. Moreover, the introduction of a ZnS overlayer on the BiVO4/PbS QDs further improved the photocurrent to 5.19 mA/cm2, attributed to the reduction in interfacial charge recombination.

Thermal Effect on Photoelectrochemical Water Splitting Toward Highly Solar to Hydrogen Efficiency.

Photoelectrochemical (PEC) hydrogen production is an emerging technology that uses renewable solar light aimed to establish a sustainable carbon-neutral society. The barriers to commercialization are low efficiency and high cost. To date, researchers have focused on materials and systems. However, recent studies have been conducted to utilize thermal effects in PEC hydrogen production. This Review provides a fresh perspective to utilize the thermal effects for PEC performance enhancement while delineating the underlying principles and equations associated with efficiency. The fundamentals of the thermal effect on the PEC system are summarized from various perspectives: kinetics, thermodynamics, and empirical equations. Based on this, materials are classified as plasmonic metals, quantum dot-based semiconductors, and photothermal organic materials, which have an inherent response to photothermal irradiation. Finally, the economic viability and challenges of these strategies for PEC are explained, which can pave the way for the future progress in the field.

Quantum Dots, Passivation Layer and Cocatalysts for Enhanced Photoelectrochemical Hydrogen Production.

Solar-driven photoelectrochemical (PEC) hydrogen production is one potential pathway to establish a carbon-neutral society. Nowadays, quantum dots (QDs)-sensitized semiconductors have emerged as promising materials for PEC hydrogen production due to their tunable bandgap by size or morphology control, displaying excellent optical and electrical properties. Nevertheless, they still suffer from anodic corrosion during long-term cycling, offering poor stability. This Review discussed advancements to improve long-term stability of QDs particularly in terms of cocatalysts and passivation layers. The working principle of PEC cells was reviewed, along with all important configurations adopted over recent years. The equations to assess PEC performance were also described. A greater emphasized was placed on QDs and incorporation of cocatalysts or passivation layers that could enhance the PEC performance by influencing the charge transfer and surface recombination processes.

Investigating the Influence of PbS Quantum Dot-Decorated TiO2 Photoanode Thickness on Photoelectrochemical Hydrogen Production Performance.

To maximize the photoelectrochemical (PEC) hydrogen production performance of quantum dot (QD)-decorated photoelectrodes, it is crucial to prioritize the optimization of electrode's structure, including thickness and porosity. In this study, we prepare PbS QD-decorated mesoporous TiO2 photoanodes for PEC hydrogen production, and systematically investigate the influence of the photoanode thickness on optical properties and PEC performances. As the thickness of photoanodes increases from 6.4 µm to 16.3 µm, the light absorption capability is enhanced across the entire visible and near-infrared (IR) spectrum due to the improved loading of PbS QDs. However, the photocurrent density is optimized for the 11.9 µm thick photoanode (15.19 mA/cm2), compared to the 6.4 µm thick (10.80 mA/cm2) and 16.3 µm thick photoanodes (11.93 mA/cm2). This optimization is attributed to the trade-off between the light absorption capability and the efficient mass transfer of the electrolyte as the photoanode thickness increases, which is confirmed by the lowest charge transfer resistance (Rct) evaluated from the electrochemical impedance data.

Effects of Mono- and Bifunctional Surface Ligands of Cu-In-Se Quantum Dots on Photoelectrochemical Hydrogen Production.

Semiconductor nanocrystal quantum dots (QDs) are promising materials for solar energy conversion because of their bandgap tunability, high absorption coefficient, and improved hot-carrier generation. CuInSe2 (CISe)-based QDs have attracted attention because of their low toxicity and wide light-absorption range, spanning visible to near-infrared light. In this work, we study the effects of the surface ligands of colloidal CISe QDs on the photoelectrochemical characteristics of QD-photoanodes. Colloidal CISe QDs with mono- and bifunctional surface ligands are prepared and used in the fabrication of type-II heterojunction photoanodes by adsorbing QDs on mesoporous TiO2. QDs with monofunctional ligands are directly attached on TiO2 through partial ligand detachment, which is beneficial for electron transfer between QDs and TiO2. In contrast, bifunctional ligands bridge QDs and TiO2, increasing the amount of QD adsorption. Finally, photoanodes fabricated with oleylamine-passivated QDs show a current density of ~8.2 mA/cm2, while those fabricated with mercaptopropionic-acid-passivated QDs demonstrate a current density of ~6.7 mA/cm2 (at 0.6 VRHE under one sun illumination). Our study provides important information for the preparation of QD photoelectrodes for efficient photoelectrochemical hydrogen generation.

Highly Efficient Photoelectrochemical Hydrogen Production Using Nontoxic CuIn1.5Se3 Quantum Dots with ZnS/SiO2 Double Overlayers.

Quantum dots (QDs) are a promising material for photoelectrochemical (PEC) hydrogen (H2) production because of their attractive optical properties including high optical absorption coefficient, band-gap tunability, and potential multiple exciton generation. To date, QDs containing toxic elements such as Cd or Pb have been mainly investigated for PEC H2 production, which cannot be utilized in practice because of the environmental issue. Here, we demonstrate a highly efficient type II heterojunction photoanode of nontoxic CuIn1.5Se3 (CISe) QDs and a mesoporous TiO2 film. In addition, ZnS/SiO2 double overlayers are deposited on the photoanodes to passivate surface defect sites on the CISe QDs, leading to the enhancement of both photocurrent density and photostability. Due to a combination of a wide light absorption range of the CISe QDs and the reduced interfacial charge recombination by the overlayers, a remarkable photocurrent density of 8.5 mA cm-2 (at 0.5 VRHE) is obtained under 1 sun illumination, which is a record for the PEC sulfite oxidation based on nontoxic QD photoanodes.

Accuracy of the Childhood Autism Rating Scale: a systematic review and meta-analysis.

AIM: To assess the accuracy of the Childhood Autism Rating Scale (CARS) through systematic review and meta-analysis. METHOD: Studies that provided quantitative values for the reliability and validity for all versions of CARS were searched through MEDLINE, CINAHL, PsycINFO, Embase, and OpenDissertations. RESULTS: A total of 24 studies with 4433 participants were included in our analysis. Meta-analysis showed that the summary Cronbach's alpha regarding a team of physicians and psychologists or others subgroup, derived from six studies (952 participants), was considered to be acceptable at 0.90 (95% confidence interval, 0.87-0.92) with moderate heterogeneity. Analysis of two 'low risk of bias' studies on the criterion validity for CARS with a cut-off of 30 and DSM-IV resulted in sensitivity of 0.86 and 0.71 and specificity of 0.79 and 0.75. INTERPRETATION: Through the results of the current systematic review and meta-analysis, the internal consistency can be considered to be acceptable for a team of physicians and psychologists or others subgroup. In terms of the criterion validity, the sensitivity was thought to be acceptable although the specificity was not, suggesting that CARS should be used along with other confirmatory tools. WHAT THIS PAPER ADDS: The Childhood Autism Rating Scale can be considered as a supplementary diagnostic tool for autism spectrum disorder.

EXACTITUD DE LA ESCALA DE CALIFICACIÓN DE AUTISMO INFANTIL (CARS): UNA REVISIÓN SISTEMÁTICA Y METAANÁLISIS: OBJETIVO: Se evalúa la exactitud de la Escala de Calificación de Autismo Infantil (CARS) a través de revisión sistemática y metaanálisis. MÉTODO: Los estudios que proporcionaron valores cuantitativos para la confiabilidad y validez de todas las versiones de CARS fueron buscados a través de MEDLINE, CINAHL, PsycINFO, Embase y Open Dissertations. RESULTADOS: En nuestro análisis se incluyeron un total de 24 estudios con 4433 participantes. El metaanálisis mostró el resumen del alfa de Cronbach basado en datos de equipos de médicos y psicólogos u otros subgrupos, derivado de seis estudios (952 participantes), fue considerado aceptable en 0,90 (intervalo de confianza del 95%, 0,87 - 0,92) con moderada heterogeneidad. El análisis de dos estudios de «bajo riesgo de sesgo¼ sobre los criterios de validez para CARS con un corte de 30 y criterios de DSM-IV, mostró una sensibilidad de 0,86 y 0,71 y especificidad de 0,79 y 0,75. INTERPRETACIÓN: Los resultados de la revisión sistemática actual y el metaanálisis demostró que la consistencia interna de CARS puede considerarse aceptable cuando es utilizado por equipos de médicos y psicólogos u otros subgrupos. En cuanto a la validez de criterio, se considero que la sensibilidad era aceptable, aunque la especificidad no lo es, sugiriendo que CARS debería utilizarse junto con otras herramientas confirmatorias.

ACURÁCIA DA ESCALA DE PONTUAÇÃO DO AUTISMO NA INFÂNCIA (CHILDHOOD AUTISM RATING SCALE -CARS): UMA REVISÃO SISTEMÁTICA E METANÁLISE: OBJETIVO: Avaliar a acurácia da Escala de Pontuação do Autismo na Infância (Childhood Autism Rating Scale -CARS) por meio de revisão sistemática e metanálise. MÉTODO: Estudos que forneceram valores de confiabilidade e validade de todas as versões da CARS foram pesquisados por meio das bases MEDLINE, CINAHL, PsycINFO, Embase, e OpenDissertations. RESULTADOS: Um total de 24 estudos com 4433 participantes foram incluídos em nossa análise. A metanálise mostrou que o resumo do alfa de Cronbach para uma equipe de médicos e psicólogos ou outros subgrupos, derivado de seis estudos (952 participantes), foi considerado aceitável a 0,90 (intervalo de confiança a 95%, 0,87-0,92) com heterogeneidade moderada. Análise de dois estudos com "baixo risco de viés" sobre a validade de critério da CARS com valor de corte de 30 e DSM-IV resultou em sensibilidade de 0,86 e 0,71 e especificidade de 0,79 and 0,75. INTERPRETAÇÃO: Por meio dos resultados da presente revisão sistemática e metanálise, a consistência interna pode ser considerada aceitável para uma equipe de médicos e psicólogos ou outros subgrupos. Em termos de validade de critério, a sensibilidade foi considerada aceitável, embora a especificidade não tenha sido, sugerindo que a CARS deva ser usada juntamente com outros instrumentos confirmatórios.

Psychometric Properties of the Internet Addiction Test: A Systematic Review and Meta-Analysis.

This article performs a systemic review of psychometric properties of Internet Addiction Test (IAT)-the most widely used tool for assessing Internet addiction in clinic and research field. Studies measuring psychometric properties of IAT (original version) were searched through MEDLINE, The Cumulative Index to Nursing and Allied Health Literature (CINAHL), PsycINFO, and Embase. A total of 25 studies including 18,421 subjects were reviewed in our study. Based on meta-analysis for internal consistency, the pooled Cronbach's alpha coefficient from college/university students with a single department subgroup was 0.90 (95percent confidence interval [CI], 0.89-0.91), and that from middle-/high-school students (older than 15 years) subgroup was 0.93 (95 percent CI, 0.92-0.93). According to test-retest analysis, the pooled Spearman's correlation coefficient from college/university students with a single department subgroup was high at 0.83 (95 percent CI, 0.81-0.85), along with low publication bias. Convergent validity showed correlation coefficients of 0.62-0.84, as compared with major tools. For construct validity, the number of factors is believed to be 1-2, only considering studies that followed the guidelines. IAT appears to have acceptable internal consistency, test-retest reliability, and convergent validity in specific groups. To verify these values, well-designed evidence-based studies assessing psychometric properties of IAT across diverse populations are warranted.

Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes.

Dye-sensitized solar cells (DSCs) are promising solar energy conversion devices with aesthetically favorable properties such as being colorful and having transparent features. They are also well-known for high and reliable performance even under ambient lighting, and these advantages distinguish DSCs for applications in window-type building-integrated photovoltaics (BIPVs) that utilize photons from both lamplight and sunlight. Therefore, investigations on bifacial DSCs have been done intensively, but further enhancement in performance under back-illumination is essential for practical window-BIPV applications. In this research, highly efficient bifacial DSCs were prepared by a combination of electropolymerized poly(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and cobalt bipyridine redox ([Co(bpy)3]3+/2+) electrolyte, both of which manifested superior transparency when compared with conventional Pt and iodide counterparts, respectively. Keen electrochemical analyses of PEDOT films verified that superior electrical properties were achievable when the thickness of the film was reduced, while their high electrocatalytic activities were unchanged. The combination of the PEDOT thin film and [Co(bpy)3]3+/2+ electrolyte led to an unprecedented power conversion efficiency among bifacial DSCs under back-illumination, which was also over 85% of that obtained under front-illumination. Furthermore, the advantage of the electropolymerization process, which does not require an elevation of temperature, was demonstrated by flexible bifacial DSC applications.

Multidimensional Anodized Titanium Foam Photoelectrode for Efficient Utilization of Photons in Mesoscopic Solar Cells.

Mesoscopic solar cells based on nanostructured oxide semiconductors are considered as a promising candidates to replace conventional photovoltaics employing costly materials. However, their overall performances are below the sufficient level required for practical usages. Herein, this study proposes an anodized Ti foam (ATF) with multidimensional and hierarchical architecture as a highly efficient photoelectrode for the generation of a large photocurrent. ATF photoelectrodes prepared by electrochemical anodization of freeze-cast Ti foams have three favorable characteristics: (i) large surface area for enhanced light harvesting, (ii) 1D semiconductor structure for facilitated charge collection, and (iii) 3D highly conductive metallic current collector that enables exclusion of transparent conducting oxide substrate. Based on these advantages, when ATF is utilized in dye-sensitized solar cells, short-circuit photocurrent density up to 22.0 mA cm-2 is achieved in the conventional N719 dye-I3- /I- redox electrolyte system even with an intrinsically inferior quasi-solid electrolyte.

Iron Oxide Photoelectrode with Multidimensional Architecture for Highly Efficient Photoelectrochemical Water Splitting.

Nanostructured metal oxide semiconductors have shown outstanding performances in photoelectrochemical (PEC) water splitting, but limitations in light harvesting and charge collection have necessitated further advances in photoelectrode design. Herein, we propose anodized Fe foams (AFFs) with multidimensional nano/micro-architectures as a highly efficient photoelectrode for PEC water splitting. Fe foams fabricated by freeze-casting and sintering were electrochemically anodized and directly used as photoanodes. We verified the superiority of our design concept by achieving an unprecedented photocurrent density in PEC water splitting over 5 mA cm-2 before the dark current onset, which originated from the large surface area and low electrical resistance of the AFFs. A photocurrent of over 6.8 mA cm-2 and an accordingly high incident photon-to-current efficiency of over 50 % at 400 nm were achieved with incorporation of Co oxygen evolution catalysts. In addition, research opportunities for further advances by structual and compositional modifications are discussed, which can resolve the low fill factoring behavior and improve the overall performance.

Highly Efficient Copper-Indium-Selenide Quantum Dot Solar Cells: Suppression of Carrier Recombination by Controlled ZnS Overlayers.

Copper-indium-selenide (CISe) quantum dots (QDs) are a promising alternative to the toxic cadmium- and lead-chalcogenide QDs generally used in photovoltaics due to their low toxicity, narrow band gap, and high absorption coefficient. Here, we demonstrate that the photovoltaic performance of CISe QD-sensitized solar cells (QDSCs) can be greatly enhanced simply by optimizing the thickness of ZnS overlayers on the QD-sensitized TiO2 electrodes. By roughly doubling the thickness of the overlayers compared to the conventional one, conversion efficiency is enhanced by about 40%. Impedance studies reveal that the thick ZnS overlayers do not affect the energetic characteristics of the photoanode, yet enhance the kinetic characteristics, leading to more efficient photovoltaic performance. In particular, both interfacial electron recombination with the electrolyte and nonradiative recombination associated with QDs are significantly reduced. As a result, our best cell yields a conversion efficiency of 8.10% under standard solar illumination, a record high for heavy metal-free QD solar cells to date.

Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells.

Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot- sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye-sensitized solar cells (DSCs), with a conversion efficiency (η) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, η = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (η = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (η = 2.80%) when applied to CdSe-based QDSCs.

Highly uniform and vertically aligned SnO2 nanochannel arrays for photovoltaic applications.

Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process. In the modified process, ultrasonication is utilized to avoid formation of partial compact layers and lateral cracks in the SnO2 nanochannel arrays. Building on this breakthrough, we first demonstrate the photovoltaic application of these vertically aligned SnO2 nanochannel arrays. These vertically aligned arrays were directly and successfully applied in quasi-solid state dye-sensitized solar cells (DSSCs) as photoanodes, yielding reasonable conversion efficiency under back-side illumination. In addition, a significantly short process time (330 s) for achieving the optimal thickness (7.0 µm) and direct utilization of the anodized electrodes enable a simple, rapid and low-cost fabrication process. Furthermore, a TiO2 shell layer was coated on the SnO2 nanochannel arrays by the atomic layer deposition (ALD) process for enhancement of dye-loading and prolonging the electron lifetime in the DSSC. Owing to the presence of the ALD TiO2 layer, the short-circuit photocurrent density (Jsc) and conversion efficiency were increased by 20% and 19%, respectively, compared to those of the DSSC without the ALD TiO2 layer. This study provides valuable insight into the development of efficient SnO2-based photoanodes for photovoltaic application by a simple and rapid fabrication process.

Completely transparent conducting oxide-free and flexible dye-sensitized solar cells fabricated on plastic substrates.

To achieve commercialization and widespread application of next-generation photovoltaics, it is important to develop flexible and cost-effective devices. Given this, the elimination of expensive transparent conducting oxides (TCO) and replacement of conventional glass substrates with flexible plastic substrates presents a viable strategy to realize extremely low-cost photovoltaics with a potentially wide applicability. To this end, we report a completely TCO-free and flexible dye-sensitized solar cell (DSSC) fabricated on a plastic substrate using a unique transfer method and back-contact architecture. By adopting unique transfer techniques, the working and counter electrodes were fabricated by transferring high-temperature-annealed TiO2 and Pt/carbon films, respectively, onto flexible plastic substrates without any exfoliation. The fabricated working electrode with the conventional counter electrode exhibited a record efficiency for flexible DSSCs of 8.10%, despite its TCO-free structure. In addition, the completely TCO-free and flexible DSSC exhibited a remarkable efficiency of 7.27%. Furthermore, by using an organic hole-transporting material (spiro-MeOTAD) with the same transfer method, solid-state flexible TCO-free DSSCs were also successfully fabricated, yielding a promising efficiency of 3.36%.

Tailoring of energy levels in D-π-A organic dyes via fluorination of acceptor units for efficient dye-sensitized solar cells.

A molecular design is presented for tailoring the energy levels in D-π-A organic dyes through fluorination of their acceptor units, which is aimed at achieving efficient dye-sensitized solar cells (DSSCs). This is achieved by exploiting the chemical structure of common D-π-A organic dyes and incorporating one or two fluorine atoms at the ortho-positions of the cyanoacetic acid as additional acceptor units. As the number of incorporated fluorine atoms increases, the LUMO energy level of the organic dye is gradually lowered due to the electron-withdrawing effect of fluorine, which ultimately results in a gradual reduction of the HOMO-LUMO energy gap and an improvement in the spectral response. Systematic investigation of the effects of incorporating fluorine on the photovoltaic properties of DSSCs reveals an upshift in the conduction-band potential of the TiO2 electrode during impedance analysis; however, the incorporation of fluorine also results in an increased electron recombination rate, leading to a decrease in the open-circuit voltage (Voc). Despite this limitation, the conversion efficiency is gradually enhanced as the number of incorporated fluorine atoms is increased, which is attributed to the highly improved spectral response and photocurrent.

Highly ordered and vertically oriented TiO2/Al2O3 nanotube electrodes for application in dye-sensitized solar cells.

The surface of long TiO2 nanotube (NT) electrodes in dye-sensitized solar cells (DSSCs) was modified without post-annealing by using atomic layer deposition (ALD) for the enhancement of photovoltage. Vertically oriented TiO2 NT electrodes with highly ordered and crack-free surface structures over large areas were prepared by a two-step anodization method. The prepared TiO2 NTs had a pore size of 80 nm, and a length of 23 µm. Onto these TiO2 NTs, an Al2O3 shell of a precisely controlled thickness was deposited by ALD. The conformally coated shell layer was confirmed by high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The open-circuit voltage (V(oc)) of the DSSCs was gradually enhanced as the thickness of the Al2O3 shell of the TiO2/Al2O3 NT electrodes was increased, which resulted from the enhanced electron lifetime. The enhanced electron lifetime caused by the energy barrier effect of the shell layer was measured quantitatively by the open-circuit voltage decay technique. As a result, 1- and 2-cycle-coated samples showed enhanced conversion efficiencies compared to the bare sample.

Enhanced photovoltaic properties and long-term stability in plasmonic dye-sensitized solar cells via noncorrosive redox mediator.

We demonstrate the localized surface plasmon resonance (LSPR) effect, which can enhance the photovoltaic properties of dye-sensitized solar cells (DSSCs), and the long-term stability of size-controlled plasmonic structures using a noncorrosive redox mediator. Gold nanoparticles (Au NPs) were synthesized with a phase transfer method based on ligand exchange. This synthetic method is advantageous because the uniformly sized Au NPs, can be mass produced and easily applied to DSSC photoanodes. The plasmonic DSSCs showed an 11% improvement of power conversion efficiency due to the incorporation of 0.07 wt % Au NPs, compared to the reference DSSCs without Au NPs. The improved efficiency was primarily due to the enhanced photocurrent generation by LSPR effect. With the cobalt redox mediator, the long-term stability of the plasmonic structures also significantly increased. The plasmonic DSSCs with cobalt(II/III) tris(2,2'-bipyridine) ([Co(bpy)3](2+/3+)) redox mediator maintained the LSPR effect with stable photovoltaic performance for 1000 h. This is, to our knowledge, the first demonstration of the long-term stability of plasmonic nanostructures in plasmonic DSSCs based on liquid electrolytes. As a result, the enhanced long-term stability of plasmonic NPs via a noncorrosive redox mediator will increase the feasibility of plasmonic DSSCs.