Enhanced Performance of I2‐Free Solid‐State Dye‐Sensitized Solar Cells with Conductive Polymer up to 6.8%

An iodine‐free solid‐state dye‐sensitized solar cell (ssDSSC) is reported here, with 6.8% energy conversion efficiency—one of the highest yet reported for N719 dye—as a result of enhanced light harvesting from the increased transmittance of an organized mesoporous TiO₂ interfacial layer and the good hole conductivity of the solid‐state‐polymerized material. The organized mesoporous TiO₂ (OM‐TiO₂) interfacial layer is prepared on large‐area substrates by a sol‐gel process, and is confirmed by scanning electron microscopy (SEM) and grazing incidence small‐angle X‐ray scattering (GISAXS). A 550‐nm‐thick OM‐TiO₂ film coated on fluorine‐doped tin oxide (FTO) glass is highly transparent, resulting in transmittance increases of 8 and 4% compared to those of the bare FTO and conventional compact TiO₂ film on FTO, respectively. The high cell performance is achieved through careful control of the electrode/hole transport material (HTM) and nanocrystalline TiO₂/conductive glass interfaces, which affect the interfacial resistance of the cell. Furthermore, the transparent OM‐TiO₂ film, with its high porosity and good connectivity, exhibits improved cell performance due to increased transmittance in the visible light region, decreased interfacial resistance ( Ω ), and enhanced electron lifetime ( τ ). The cell performance also depends on the conductivity of HTMs, which indicates that both highly conductive HTM and the transparent OM‐TiO₂ film interface are crucial for obtaining high‐energy conversion efficiencies in I₂‐free ssDSSCs.     

Dye‐sensitized TiO2 solar cells based on nanocomposite photoanode containing plasma‐modified multi‐walled carbon nanotubes

A series of anatase TiO₂‐based nanocomposite incorporated with plasma‐modified multi‐walled carbon nanotubes (MWNTs) was prepared by physical blending and shows its capability for efficient electron transport when used as photoanode in dye‐sensitized solar cells (DSSCs). These MWNTs characterized with good dispersal performance were obtained by functionalization technique via in situ plasma treatment and subsequent grafting with maleic anhydride (MA) onto the external walls reported previously. Compared with the conventional DSSCs, the TiO₂ film with 1D carbon nanotubes possesses more outstanding ability to transport electrons injected from the excited dye within the device under illumination. As a result, at an optimum addition of 0.3 wt% MWNTs‐MA in TiO₂ matrix, the photocurrent–voltage (J–V) characteristics showed a significant increase in the short‐circuit photocurrent (J_sc) of 50%, leading to an increase in overall solar conversion efficiency by a factor of 1.5. Electrochemical impedance spectroscopy analyses reveal that the MWNTs‐MA/TiO₂ incur smaller resistances at the photoanode in assembled DSSCs when compared with those in the anatase titania DSSCs. These features suggest that the conducting properties of the MWNTs‐MA within the anodes are crucial for achieving a higher transport rate for photo‐induced electrons in TiO₂ layer by exhibiting lower resistance in the porous network and hence retard charge recombination that could result in poor conversion efficiency. Copyright © 2012 John Wiley & Sons, Ltd.     

Enhancing the Performance of Solid‐State Dye‐Sensitized Solar Cells Using a Mesoporous Interfacial Titania Layer with a Bragg Stack

High efficiency dye‐sensitized solar cells (DSSCs) are fabricated with a heterostructured photoanode that consists of a 500‐nm‐thick organized mesoporous TiO₂ (om‐TiO₂) interfacial layer (IF layer), a 7 or 10‐μm thick nanocrystalline TiO₂ layer (NC layer), and a 2‐μm‐thick mesoporous Bragg stack (meso‐BS layer) as the bottom, middle and top layers, respectively. An om‐TiO₂ layer with a high porosity, transmittance, and interconnectivity is prepared via a sol‐gel process, in which a poly(vinyl chloride)‐g‐poly(oxyethylene methacrylate) (PVC‐g‐POEM) graft copolymer is used as a structure‐directing agent. The meso‐BS layer with large pores is prepared via alternating deposition of om‐TiO₂ and colloidal SiO₂ (col‐SiO₂) layers. Structure and optical properties (refractive index) of the om‐TiO₂ and meso‐BS layers are studied and the morphology of the heterostructured photoanode is characterized. DSSCs fabricated with the heterostructured IF/NC/BS photoanode and combined with a polymerized ionic liquid (PIL) exhibit an energy conversion efficiencies of 6.6% at 100 mW/cm², one of the highest reported for solid‐state DSSCs and much larger than cells prepared with only a IF/NC layer (6.0%) or a NC layer (4.5%). Improvements in energy conversion efficiency are attributed to the combination of improved light harvesting, decreased resistance at the electrode/electrolyte interface, and excellent electrolyte infiltration.     

Design of conduction band structure of TiO2 electrode using Nb doping for highly efficient dye‐sensitized solar cells

A barrier layer of undoped TiO₂ was deposited on the Nb‐doped TiO₂ electrode to suppress the recombination at the Nb‐doped TiO₂/dye–electrolyte interface for highly efficient dye‐sensitized solar cells (DSCs). The Nb content in TiO₂ was varied in a range of 0.7–3.5 mol% to modify the TiO₂ energy‐band structure. Nb‐doped TiO₂/dye interfaces were characterized by a combination of ultraviolet photoemission spectroscopy and optical absorption spectroscopy measurements, allowing the determination of the conduction band minimum (CBM) of the TiO₂ electrode and the lowest unoccupied molecular orbital of the N719 dye. The lowering of TiO₂ CBM by Nb doping induced the increase in short‐circuit current of DSCs. However, open‐circuit voltage and fill factor are decreased, and this result was ascribed to the enhanced recombination at the Nb‐doped TiO₂/dye–electrolyte interface. The effect of doping on charge transport in DSCs was analyzed using electrochemical impedance spectroscopy. We have shown that by introducing of TiO₂ barrier layer, the Nb doping content, which results in DSC highest efficiency, can be increased because of the suppression of the dopant‐induced recombination. The energy conversion efficiency of the solar cells increased from 7.8% to 9.0% when undoped TiO₂ electrode is replaced with electrode doped with 2.7 mol% of Nb because of the improvement of the electron injection and collection efficiencies. The correlation between the electronic structure of the TiO₂ electrode, charge transfer characteristics, and photovoltaic parameters of DSCs is discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

An efficient titanium‐based photoanode for dye‐sensitized solar cell under back‐side illumination

Pretreatment of H₂O₂ is performed on titanium (Ti) foil as an efficient photoanode substrate for dye‐sensitized solar cell (DSSC). The H₂O₂‐treated Ti shows high surface area because of the formation of networked TiO₂ nanosheets, which enhances electrical contact between screen‐printed TiO₂ nanoparticles and Ti foil. Electron transfer on the photoanode is improved, as identified by reduced charge transfer resistance and improved electron transport properties. Compared with DSSC based on non‐treated Ti photoanode, DSSC with this H₂O₂‐treated Ti photoanode exhibits remarkable increases in short‐circuit current density (from 8.55 to 14.38 mA/cm²) and energy conversion efficiency (from 4.68 to 7.10%) under AM1.5 back‐side illumination. Copyright © 2011 John Wiley & Sons, Ltd.     

Honeycomb‐Like Organized TiO2 Photoanodes with Dual Pores for Solid‐State Dye‐Sensitized Solar Cells

A solid‐state dye‐sensitized solar cell (ssDSSC) with 7.4% efficiency at 100 mW/cm² is reported. This efficiency is one of the highest observed for N719 dye. High performance is achieved via a honeycomb‐like, organized mesoporous TiO₂ photoanode with dual pores, high porosity, good interconnectivity, and excellent light scattering properties. The TiO₂ photoanodes are prepared without any TiCl₄ treatment via a one‐step, direct self‐assembly of hydrophilically preformed TiO₂ nanocrystals and poly(vinyl chloride)‐g‐poly(oxyethylene methacrylate) (PVC‐g‐POEM) graft copolymer as a titania source and a structure‐directing agent, respectively. Upon controlling the secondary forces between the polymer/TiO₂ hybrid and the solvent by varying the amounts of HCl/H₂O mixture or toluene, honeycomb‐like structures are generated to improve light scattering properties. Such multifunctional nanostructures with dual pores provide good pore‐filling of solid polymer electrolyte with large volume, enhanced light harvesting and reduced charge recombination, as confirmed by reflectance spectroscopy, incident photon‐to‐electron conversion efficiency (IPCE), and electrochemical impedance spectroscopy (EIS) analysis.     

Effectively Utilizing NIR Light Using Direct Electron Injection from Up‐Conversion Nanoparticles to the TiO2 Photoanode in Dye‐Sensitized Solar Cells

TiO₂/NaYF₄:Yb³⁺,Er³⁺ nano‐heterostructures are prepared in situ on the TiO₂ photoanode of dye‐sensitized solar cells (DSCs). Transmission electron microscopy (TEM) and high‐resolution (HR)‐TEM confirm the formation of TiO₂/NaYF₄:Yb³⁺,Er³⁺ nano‐heterostructures. The up‐converted fluorescence spectrum of the photoanode containing the nano‐heterostructure confirms electron injection from NaYF₄:Yb³⁺,Er³⁺ to the condution band (CB) of TiO₂. When using a photoanode containing the nano‐heterostructure in a DSC, the overall efficiency (η) of the device is 17% higher than that of a device without the up‐conversion nanoparticles (UCNPs) and 13% higher than that of a device containing mixed TiO₂ and UCNPs. Nano‐heterostructures of TiO₂/NaYF₄:Yb³⁺,Tm³⁺ and TiO₂/NaYF₄:Yb³⁺,Ho³⁺ can also be prepared in situ on TiO₂ photoanodes. The overall efficiency of the device containing TiO₂/NaYF₄:Yb³⁺,Ho³⁺ nano‐heterostructures is 15% higher than the control device without UCNPs. When nano‐heterostructures of TiO₂/NaYF₄:Yb³⁺,Tm³⁺ are used, the open‐circuit voltage (V_oc) and the short‐circuit current density (J_sc) are all slightly decreased. The effect of the different UCNPs results from the different energy levels of Er³⁺, Tm³⁺, and Ho³⁺. These results demonstrate that utilizing the UCNPs with the apporpriate energy levels can lead to effective electron injection from the UCNPs to the CB of TiO₂, effectively improving the photocurrent and overall efficiency of DSCs while using NIR light.     

Low‐temperature flexible Ti/TiO2 photoanode for dye‐sensitized solar cells with binder‐free TiO2 paste

An energy‐economical dye‐sensitized solar cell (DSSC) with highly flexible Ti/TiO₂ photoanode was developed through a low‐temperature process, using a binder‐free TiO₂ paste. Ti foils, coated with the binder‐free TiO₂ films were annealed at various temperature. Scanning electron microscopic (SEM) images of the films show uniform, mesoporous and crack‐free surface morphologies as well as interpenetrated TiO₂ network. DSSCs with binder‐free TiO₂ films annealed at 450, 350, 250 and 120°C show solar‐to‐electricity conversion efficiencies (η) of 4.33, 4.34, 3.72 and 3.40%, respectively, which are comparable to the efficiency of 4.56% obtained by using a paste with binder and annealing it at 450°C; this observation demonstrates the benefits of a binder‐free TiO₂ paste for the fabrication of energy‐fugal DSSCs. On the other hand, when organic binder was used in the TiO₂ paste for film preparation, a drastic deterioration in the cell performance with decreasing annealing temperature is noticed. Laser‐induced photo‐voltage transient technique is used to estimate the electron lifetime in various Ti/TiO₂ films. Electrochemical impedance spectroscopic (EIS) analysis shows that the lower the annealing temperature of the TiO₂ coated Ti foil, the larger the charge transfer resistance at the TiO₂/dye/electrolyte interface (R_ct2). Copyright © 2011 John Wiley & Sons, Ltd.     

Piezoelectric‐Effect‐Enhanced Full‐Spectrum Photoelectrocatalysis in p–n Heterojunction

Photoelectrochemical (PEC) water splitting offers a promising strategy for converting solar energy to chemical fuels. Herein, a piezoelectric‐effect–enhanced full‐spectrum photoelectrocatalysis with multilayered coaxial titanium dioxide/barium titanate/silver oxide (TiO₂/BTO/Ag₂O) nanorod array as the photoanode is reported. The vertically grown nanorods ensure good electron conductivity, which enables fast transport of the photogenerated electrons. Significantly, the insertion of a piezoelectric BaTiO₃ (BTO) nanolayer at the p‐type Ag₂O and n‐type TiO₂ interface created a polar charge‐stabilized electrical field. It maintains a sustainable driving force that attract the holes of TiO₂ and the electrons of Ag₂O, resulting in greatly increased separation and inhibited recombination of the photogenerated carriers. Furthermore, Ag₂O as a narrow bandgap semiconductor has a high ultraviolet–visible–near infrared (UV–vis–NIR) photoelectrocatalytic activity. The TiO₂/BTO/Ag₂O, after poling, successfully achieves a prominent photocurrent density, as high as 1.8 mA cm^?2 at 0.8 V versus Ag/Cl, which is about 2.6 times the TiO₂ nanorod photoanode. It is the first time that piezoelectric BaTiO₃ is used for tuning the interface of p‐type and n‐type photoelectrocatalyst. With the enhanced light harvesting, efficient photogenerated electron–hole pairs' separation, and rapid charge transfer at the photoanode, an excellent photoelectrocatalytic activity is realized.     

Metal–Organic Framework Derived Narrow Bandgap Cobalt Carbide Sensitized Titanium Dioxide Nanocage for Superior Photo‐Electrochemical Water Oxidation Performance

Despite recent progress in photo‐electrochemical (PEC) water oxidation systems for TiO₂‐based photoanodes, PEC performance improvement is still seriously hampered due to poor carrier transport efficiency and sluggish surface water oxidation kinetics of pristine TiO₂. Herein, for the first time a brand new metal–organic framework (MOF)‐derived Co₃C nanosheet with narrow bandgap energy is demonstrated, to effectively sensitize TiO₂ hollow cages as a heterostructure photoanode for PEC water oxidation. It is found that MOF‐derived Co₃C nanosheet with narrow bandgap characteristic can simultaneously accelerate the surface water oxidation kinetics and extend the light harvesting range of pristine TiO₂. Meanwhile, a uniquely matched type‐II heterojunction constructed between MOF‐derived Co₃C and TiO₂ results in an evidently spontaneous e^?/h⁺ separation. MOF‐derived Co₃C/TiO₂ heterostructure photoanodes bring about drastically improved PEC water oxidation performance. Specifically, MOF‐derived Co₃C‐3/TiO₂ photoanode with an optimized content of Co₃C achieves the highest photocurrent density and charge separation efficiency of 2.6 mA cm^?2 and 92.6% at 1.23 V versus reversible hydrogen electrode, corresponding to 201% and 152% improvement compared with pristine TiO₂ nanocages. The ingeniously prepared MOF‐derived Co₃C carbide with narrow bandgap energy as a cocatalyst paves new way to construct potentially high performance solar‐energy conversion system.     

Multistep hydrothermal route for nanocoral architecture of anatase TiO2: synthesis and characterization of dye‐sensitized solar cell performance

Multistep hydrothermal (MSH) process is employed for growth of TiO₂ nanocorals onto the conducting fluorine‐doped tin oxide‐coated glass substrates. The surface morphological features and physical properties of TiO₂ films were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, room temperature photoluminescence spectroscopy and X‐ray photoelectron spectroscopy. The surface morphology revealed the formation of TiO₂ corals having nanosized (30–40 nm) polyps. The photoelectrochemical properties of the TiO₂ nanocoral electrodes were investigated in 0.1 M NaOH electrolyte under ultraviolet illumination. The results presented in this study highlight two major findings: (i) tuning the photoelectrochemical response and photoconversion efficiency via controlled thickness of TiO₂ nanocorals by MSH route and (ii) the substantial increase in short‐circuit photocurrent (J_sc) because of the improved charge transport through TiO₂ nanocorals prepared via MSH process. Copyright © 2012 John Wiley & Sons, Ltd.     

The 2,2,6,6‐Tetramethyl‐1‐piperidinyloxy Radical: An Efficient,Iodine‐ Free Redox Mediator for Dye‐Sensitized Solar Cells

A promising redox system, offering an alternative to the widely used iodide/triiodide couple, based on the stable organic radical 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) has been employed in dye‐sensitized solar cells. The photovoltaic performance of this new redox couple has been evaluated by employing nanocrystalline TiO₂ films with different thickness. Judicious selections of a 5.0 μm photoanode made from TiO₂ mesoscopic particles and an organic sensitizer with a high molar extinction coefficient yield an overall solar‐to‐electric power conversion efficiency of 5.4 % under AM 1.5 illumination at 100 mW cm^–2, which is unprecedented for an iodine‐free mediator system.     

A Novel Photocathode Material for Sunlight‐Driven Overall Water Splitting: Solid Solution of ZnSe and Cu(In,Ga)Se2

Thin films of a solid solution of ZnSe and CuIn_0.7Ga_0.3Se₂ ((ZnSe) _x (CIGS) _1–x ) are prepared by co‐evaporation. Structural characterization reveals that the ZnSe and CIGS form a solid solution with no phase separation. (ZnSe)_0.85(CIGS)_0.15‐based photocathodes modified with Pt, Mo, Ti, and CdS exhibit a photocurrent of 7.1 mA cm^?2 at 0 V_RHE, and a relatively high onset potential of 0.89 V_RHE under simulated sunlight. A two‐electrode cell containing a (ZnSe)_0.85(CIGS)_0.15 photocathode and a BiVO₄‐based photoanode has an initial solar‐to‐hydrogen conversion efficiency of 0.91%, which is one of the highest values reported for a photoanode–photocathode combination. Thus, (ZnSe)_0.85(CIGS)_0.15 is a promising photocathode material for efficient photoelectrochemical water splitting.     

In situ preparation of hierarchically structured dual-layer TiO2 films by E-spray method for efficient dye-sensitized solar cells

Hierarchically-structured mesoporous TiO₂ films are prepared by the electrospray (E-spray) method. The microstructures of TiO₂ films can be feasibly tuned as spheres or nanocrystalline-mixed spheres, rendering in situ preparation of TiO₂ dual-layer. With these dual-layer TiO₂ films as photoanode and N719 as sensitizer, the dye-sensitized solar cell achieves a power conversion efficiency (PCE) of 8.96%, which is among the best of N719 devices so far, and constituting up to 19% improvement relative to single-layer TiO₂ photoanode based devices. To disclose the mechanism for the improvement, corresponding samples are prepared and investigated by scanning electron microscopy, electrochemical impedance spectroscopy, diffuse reflectance spectra. It was found that the dual-layer photoanode can simultaneously incorporate high dye loading and low charge transfer resistance, leading to high short current density and thus high PCE. Different to other reported dual-layer photoanodes, which often need two or more preparing procedures, only one step is needed in this work. To our best knowledge, it is the first time to employ only one step to in situ prepare photoanodes with dual-layer structures, which greatly simplifies the experimental processes.     

Solution Processing Route to Multifunctional Titania Thin Films: Highly Conductive and Photcatalytically Active Nb:TiO2

This paper reports the synthesis of highly conductive niobium doped titanium dioxide (Nb:TiO₂) films from the decomposition of Ti(OEt)₄ with dopant quantities of Nb(OEt)₅ by aerosol‐assisted chemical vapor deposition (AACVD). Doping Nb into the Ti sites results in n‐type conductivity, as determined by Hall effect measurements. The doped films display significantly improved electrical properties compared to pristine TiO₂ films. For 5 at.% Nb in the films, the charge carrier concentration was 2 × 10²¹ cm^?3 with a mobility of 2 cm² V^–1 s^–1 . The corresponding sheet resistance is as low as 6.5 Ω sq^–1 making the films suitable candidates for transparent conducting oxide (TCO) materials. This is, to the best of our knowledge, the lowest reported sheet resistance for Nb:TiO₂ films synthesized by vapour deposition. The doped films are also blue in colour, with the intensity dependent on the Nb concentration in the films. A combination of synchrotron, laboratory and theoretical techniques confirmed niobium doping into the anatase TiO₂ lattice. Computational methods also confirmed experimental results of both delocalized (Ti⁴⁺) and localized polaronic states (Ti³⁺) states. Additionally, the doped films also functioned as photocatalysts. Thus, Nb:TiO₂ combines four functional properties (photocatalysis, electrical conductivity, optical transparency and blue colouration) within the same layer, making it a promising alternative to conventional TCO materials.     

Enhanced Photocatalytic Activity using Layer‐by‐Layer Electrospun Constructs for Water Remediation

Endocrine disruptors such as bisphenol A (BPA) are environmental pollutants that interfere with the body's endocrine system because of their structural similarity to natural and synthetic hormones. Due to their strong oxidizing potential to decompose such organic pollutants, colloidal metal oxide photocatalysts have attracted increasing attention for water detoxification. However, achieving both long‐term physical stability and high efficiency simultaneously with such photocatalytic systems poses many challenges. Here a layer‐by‐layer (LbL) deposition approach is reported for immobilizing TiO₂ nanoparticles (NPs) on a porous support while maintaining a high catalytic efficiency for photochemical decomposition of BPA. Anatase TiO₂ NPs ≈7 nm in diameter self‐assemble in consecutive layers with positively charged polyhedral oligomeric silsesquioxanes on a high surface area, porous electrospun polymer fiber mesh. The TiO₂ LbL nanofibers decompose approximately 2.2 mg BPA per mg of TiO₂ in 40 h of illumination (AM 1.5G illumination), maintaining first‐order kinetics with a rate constant (k) of 0.15 h^?1 for over 40 h. Although the colloidal TiO₂ NPs initially show significantly higher photocatalytic activity (k ≈ 0.84 h^?1), the rate constant drops to k ≈ 0.07 h^?1 after 4 h of operation, seemingly due to particle agglomeration. In the BPA solution treated with the multilayered TiO₂ nanofibers for 40 h, the estrogenic activity, based on human breast cancer cell proliferation, is significantly lower than that in the BPA solution treated with colloidal TiO₂ NPs under the same conditions. This study demonstrates that water‐based, electrostatic LbL deposition effectively immobilizes and stabilizes TiO₂ NPs on electrospun polymer nanofibers for efficient extended photochemical water remediation.     

Enhanced Light‐Harvesting and Photocatalytic Properties in Morph‐TiO2 from Green‐Leaf Biotemplates

The unique structure of green leaves endows them with an extremely high light‐harvesting efficiency. In this work, green leaves are applied as biotemplates to synthesize morph‐TiO₂. The structural features favorable for light harvesting from the macro‐ to the nanoscale are replicated in morph‐TiO₂ through a two‐step infiltration process and the N contained in the original leaves is self‐doped into the resulting samples. The absorbance intensities within the visible‐light range of morph‐TiO₂ derived from different leaves increase by 103–258% and the band‐gap‐absorption onsets at the edge of the UV and visible‐light range show a red‐shift of 25–100 nm compared to those in TiO₂ without the template. The photocatalytic activity of morph‐TiO₂ is also improved, as proven by an electron paramagnetic resonance (EPR) study and degradation of rhodamine dye under irradiation with UV and visible light. The present work, as a new strategy, is of far‐reaching significance in learning from nature, driving us to make full use of the most‐abundant resources and structure‐introduced functions endowed by nature, opening up possibilities for extensive study of the physical and chemical properties of morph‐structured oxides and extending their potential for use in applications such as solar cells, photocatalysts, photoelectrical devices, and photoinduced sensors.     

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co₃O₄‐modified TiO₂ nanorod array grown on Si (MOFs‐derived Co₃O₄/TiO₂/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co₃O₄/TiO₂/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO₂ and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO₂, the photogenerated electrons from TiO₂ will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO₂ at the TiO₂/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO₂ and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co₃O₄ obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co₃O₄/TiO₂/FTO photoanode, the synergistic function in the MOFs‐derived Co₃O₄/TiO₂/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm^?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.     

Creating an Air‐Stable Sulfur‐Doped Black Phosphorus‐TiO2 Composite as High‐Performance Anode Material for Sodium‐Ion Storage

With the increasing demand for low cost, long lifetime, high energy density storage systems, an extensive amount of effort has recently been focused on the development of sodium‐ion batteries (SIBs), and a variety of cathode materials have been discovered. However, looking for the most suitable anode material for practical application is a major challenge for SIBs. Herein, a high capacity sulfur‐doped black phosphorus‐TiO₂ (TiO₂‐BP‐S) anode material for SIBs is first synthesized by a feasible and large‐scale high‐energy ball‐milling approach, and its stability in air exposure is investigated through X‐ray photoelectron spectroscopy. The morphology of TiO₂‐BP‐S is characterized using transmission electron microscopy, indicating that the TiO₂ nanoparticles produce P? Ti bonds with BP. The TiO₂‐BP‐S composite with P? S and P? Ti bonds exhibits excellent stability in air and the superior electrochemical performance. For example, the discharge specific capacity is up to 490 mA h g^?1 after 100 cycles at 50 mA g^?1, and it remains at 290 mA h g^?1 after 600 cycles at 500 mA g^?1. Meanwhile, the scientific insight that the formation of stable P? S and P? Ti bonds can provide a guide for the practical large‐scale application of SIBs in other titanium base and black phosphorus materials is looked forward.     

Development of Nano‐TiO2 dye sensitised solar cells on high mobility transparent conducting oxide thin films

The optical transmission of dye‐sensitised solar cells (DSCs) can be tuned by altering the dye and/or particle size of the mesoporous TiO₂ layers, to allow their application as the top device in tandem solar cells. To benefit from this semi‐transparency, parasitic optical losses by the transparent electrodes must be minimised. This work investigates the influence of using two different transparent conductors, namely, the high mobility material titanium doped indium oxide (ITiO) and fluorine doped tin oxide (FTO) as electrodes for semi‐transparent DSCs. The overall NIR transparency through the DSCs increased significantly as each FTO electrode was replaced by an ITiO electrode. This increase was from 20–45% in the 1300–700 nm wavelength range for fully FTO‐based cells, to about 60% for fully ITiO‐based cells, across the same spectrum. DSCs prepared on these electrodes exhibited short circuit currents ranging from 14·0–14·9 mA/cm². The conversion efficiency of the cell with ITiO as both the front and rear electrodes was 5·8%, which though significant, was lower than the 8·2% attained by the cell using FTO electrodes, as a result of a lower fill factor. Improvements in the ITiO thermal stability and in the processing of the TiO₂ interfacial layer are expected to improve the cell efficiency of such single DSC devices. The high current density and optical transparency of ITiO‐based DSCs make them an interesting option for tandem solar cells. Copyright © 2008 John Wiley & Sons, Ltd.