Dye-sensitized solar cells based on WO3

In research on alternative photoanode materials for dye-sensitized solar cells (DSCs), there is rarely any report on WO(3), probably due to its acidic surface and more positive (vs NHE) conduction band edge position compared to TiO(2) and ZnO. For the first time, dye-sensitized solar cells based on porous WO(3) nanoparticle films were successfully fabricated with efficiency of up to 0.75%. The multicrystalline structure of WO(3) was examined by Raman spectroscopy and X-ray diffraction analysis. It was found that significant performance enhancement can be obtained from treating the WO(3) nanoparticle film with TiCl(4); the TiCl(4)-treated WO(3) DSCs were recorded with efficiency reaching 1.46%.     

Double-layer coating of SrCO3/TiO2 on nanoporous TiO2 for efficient dye-sensitized solar cells

Surface modification plays a crucial role in improving the efficiency of dye-sensitized solar cells (DSSCs), but the reported surface treatments are in general superior to the untreated TiO(2) but inferior to the typical TiCl(4)-treated TiO(2) in terms of solar cell performance. This work demonstrates a two-step treatment of the nanoporous titania surface with strontium acetate [Sr(OAc)(2)] and TiCl(4) in order, each step followed by sintering. An electronically insulating layer of SrCO(3) is formed on the TiO(2) surface via the Sr(OAc)(2) treatment and then a fresh TiO(2) layer is deposited on top of the SrCO(3) layer via the TiCl(4) treatment, corresponding to a double layer of Sr(OAc)(2)/TiO(2) coated on the TiO(2) surface. As compared to the typical TiCl(4)-treated DSSC, the Sr(OAc)(2)-TiCl(4) treated DSSC improves short-circuit photocurrent (J(sc)) by 17%, open-circuit photovoltage (V(oc)) by 2%, and power conversion efficiency by 20%. These results indicate that the Sr(OAc)(2)-TiCl(4) treatment is better than the often used TiCl(4) treatment for fabrication of efficient DSSCs. Charge density at open circuit and controlled intensity modulated photocurrent/photovoltage spectroscopy reveal that the two electrodes show almost same conduction band level but different electron diffusion coefficient and charge recombination rate constant. Owing to the blocking effect of the SrCO(3) layer on electron recombination with I(3)(-) ions, the charge recombination rate constant of the Sr(OAc)(2)-TiCl(4) treated DSSC is half that of the TiCl(4)-treated DSSC, accounting well for the difference of their V(oc). The improved J(sc) is also attributed to the middle SrCO(3) layer, which increases dye adsorption and may improve charge separation efficiency due to the blocking effect of SrCO(3) on charge recombination.     

A simple recipe for an efficient TiO2 nanofiber-based dye-sensitized solar cell

Development of highly efficient dye-sensitized solar cells (DSSCs) with good photovoltaic parameters is an active research area of current global interest. In this article, we provide a simple recipe for the fabrication of electrospun TiO(2) nanorod-based efficient dye-sensitized solar cell using a Pechini-type sol. The Pechini-type sol of TiO(2) nanofibers produces a highly porous and compact layer of TiO(2) upon doctor-blading and sintering without the need for an adhesion and scattering layers or TiCl(4) treatment. The best nanofiber DSSCs with an area of ~0.28 cm(2) shows an efficiency of ~4.2% under standard test conditions (100 mW/cm(2), 25°C and AM1.5 G) and an incident photon-to-electron conversion efficiency (IPCE) of ~50%. Impedance measurements show lower charge transfer resistance that improved the fill factor. We believe that simple approaches such as the present one to develop nanofiber DSSCs would open up enormous possibilities in effective harvesting of solar energy for commercial applications, considering the fact that electrospinning is a cost-effective method for the mass scale production of nanofibers and nanorods.     

A novel photoanode architecture of dye-sensitized solar cells based on TiO2 hollow sphere/nanorod array double-layer film

A novel TiO(2) double-layer (DL) film consisting of TiO(2) hollow spheres (HSs) as overlayer and single-crystalline TiO(2) nanorod arrays (RAs) as underlayer was designed as the photoanode of dye-sensitized solar cells (DSSCs). This new-typed TiO(2) HS/RA DL film could significantly improve the efficiency of DSSCs owing to its synergic effects, i.e. the relatively large specific surface area of TiO(2) HSs for effective dye adsorption, enhanced light harvesting capability originated from TiO(2) RA film, and rapid interfacial electron transport in one-dimensional TiO(2) nanorod arrays. The overall energy-conversion efficiency of 4.57% was achieved by the formation of TiO(2) DL film, which is 16% higher than that formed by TiO(2) HS film and far larger than that formed by TiO(2) RA film (η=0.99%). The light absorption and interfacial electron transport, which play important roles in the efficiency of DSSCs, were investigated by UV-vis absorption spectra and electrochemical impedance spectra.     

Fabrication and photovoltaic performance of hierarchically titanate tubular structures self-assembled by nanotubes and nanosheets

Hierarchically macro-/mesoporous titanate tubular structures (HTT) self-assembled by nanotubes and nanosheets were fabricated by hydrothermal treatment of titanate glycolate rods in 0.1 M NaOH aqueous solution. Double-layered dye-sensitized solar cells (DSSCs) composed of a P25 nanoparticle (NP) underlayer and a tubular TiO(2) overlayer demonstrated an enhanced photovoltaic conversion efficiency of 6.2%.     

Dye-sensitized solar cells based on TiO2-B nanobelt/TiO2 nanoparticle sandwich-type photoelectrodes with controllable nanobelt length

The TiO(2)-B nanobelt (NB)/TiO(2) nanoparticle (NP) sandwich-type structure photoelectrode, with controllable nanobelt length, has been used to fabricate high-efficiency dye-sensitized solar cells (DSSCs), which combine the advantages of the rapid electron transport in TiO(2)-B NBs and the high surface area of TiO(2) NPs. The results indicate that the sandwich-type photoelectrode achieves higher photoelectrical conversion efficiency when compared with the TiO(2) nanoparticulate electrode. Increasing the length of TiO(2)-B NBs has been demonstrated to improve the photoelectric conversion efficiency (η). DSSCs with the longest (10 μm) TiO(2)-B NBs yield the highest η of 7.94%. The interfacial electron transport of DSSCs with different lengths of TiO(2)-B NBs has been quantitatively investigated using the photovoltage transient and the electrochemical impedance spectra, which demonstrates that the DSSCs with longest TiO(2)-B NBs display the highest electron collection efficiency and the fastest interfacial electron transfer.     

Porous copper zinc tin sulfide thin film as photocathode for double junction photoelectrochemical solar cells

Porous copper zinc tin sulfide (CZTS) thin film was prepared via a solvothermal approach. Compared with conventional dye-sensitized solar cells (DSSCs), double junction photoelectrochemical cells using dye-sensitized n-type TiO(2) (DS-TiO(2)) as the photoanode and porous p-type CZTS film as the photocathode shows an increased short circuit current, external quantum efficiency and power conversion efficiency.     

Reconstruction of the (001) surface of TiO2 nanosheets induced by the fluorine-surfactant removal process under UV-irradiation for dye-sensitized solar cells

The champion dye-sensitized solar cells (DSSCs) based on TiO(2) nanoparticles nearly reach the limit of photo-current density using the black dye or zinc porphyrin dye as sensitizer. However, the way to make ordinary DSSCs more efficient as well as to understand the mechanism is still essential. Here we present an elegant UV irradiation treatment of TiO(2) nanosheets to enhance the performance of DSSCs based on the TiO(2) nanosheets via room temperature removal of inorganic surfactants and reconstruction of the (001) surface of TiO(2) nanosheets, killing two birds with one stone. UV irradiation was utilized to remove the fluorine-surfactant on the surface of anatase TiO(2) nanosheets with a high percentage of exposed {001} facets which were synthesized with the aid of hydrofluoric acid. The nanosheets treated with UV irradiation for 40 min had the advantage of improving the photoelectric conversion efficiency of DSSCs by 17.6%, compared to that without UV treatment when they were introduced into DSSCs as photoanode materials. The improved efficiency was ascribed to more dye adsorption. A theoretical calculation proposed that UV irradiation induced microfaceted steps on the TiO(2) surface by two domain (1 × 4) reconstruction after UV irradiating the (1 × 1) (001) surface. The microfaceted steps increase the active surface area of the TiO(2) nanosheets by increasing the exposure of titanium atoms and engendering active sites.     

Synthesis of anatase TiO2 rods with dominant reactive {010} facets for the photoreduction of CO2 to CH4 and use in dye-sensitized solar cells

Single crystalline anatase TiO(2) rods with dominant reactive {010} facets are directly synthesized by hydrothermally treating Cs(0.68)Ti(1.83)O(4)/H(0.68)Ti(1.83)O(4) particles. The nanosized rods show a comparable conversion efficiency in dye-sensitized solar cells (DSSCs), and a superior photocatalytic conversion of CO(2) into methane to the benchmark P25 TiO(2) nanocrystals.     

A convenient route to high area, nanoparticulate TiO2 photoelectrodes suitable for high-efficiency energy conversion in dye-sensitized solar cells

Ethanol-soluble amphiphilic TiO(2) nanoparticles (NPs) of average diameter ～9 nm were synthesized, and an α-terpineol-based TiO(2) paste was readily prepared from them in comparatively few steps. When used for fabrication of photoelectrodes for dye-sensitized solar cells (DSSCs), the paste yielded highly transparent films and possessing greater-than-typical, thickness-normalized surface areas. These film properties enabled the corresponding DSSCs to produce high photocurrent densities (17.7 mA cm(-2)) and a comparatively high overall light-to-electrical energy conversion efficiency (9.6%) when deployed with the well-known ruthenium-based molecular dye, N719. These efficiencies are about ～1.4 times greater than those obtained from DSSCs containing photoelectrodes derived from a standard commercial source of TiO(2) paste.     

Ni3S4@C/CNFs对电极膜厚对染料敏化太阳能电池光伏性能的影响

采用静电纺丝技术和水热法合成了负载于碳纳米纤维表面的碳包覆Ni3S4纳米颗粒(Ni3S4@C/CNFs),利用喷涂法制备膜厚分别为2、4、6、7、8、9、10μm的Ni3S4@C/CNFs对电极。应用到染料敏化太阳能电池(DSSCs)中,探究Ni3S4@C/CNFs对电极的膜厚对于DSSCs光伏性能的影响。最终得出当Ni3S4@C/CNFs对电极膜厚为9μm时,DSSCs可以获得最高的光电转换效率(PCE)8.45%,也证明了对电极存在一个最佳膜厚,使DSSCs获得最优的光伏性能。     

The importance of dye chemistry and TiCl(4) surface treatment in the behavior of Al(2)O(3) recombination barrier layers deposited by atomic layer deposition in solid-state dye-sensitized solar cells

Atomic layer deposition (ALD) was used to fabricate Al(2)O(3) recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al(2)O(3) recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-thick nanoporous TiO(2) active layer and the HTM spiro-OMeTAD. The impact of Al(2)O(3) barriers was also studied in devices employing different dyes, with increased active layer thicknesses, and with substrates that did not undergo the TiCl(4) surface treatment. In all instances, electron lifetimes (as determined by transient photovoltage measurements) increased and dark current was suppressed after Al(2)O(3) deposition. However, only when the TiCl(4) treatment was eliminated did device efficiency increase; in all other instances efficiency decreased due to a drop in short-circuit current. These results are attributed in the former case to the similar effects of Al(2)O(3) ALD and the TiCl(4) surface treatment whereas the insulating properties of Al(2)O(3) hinder charge injection and lead to current loss in TiCl(4)-treated devices. The impact of Al(2)O(3) barrier layers was unaffected by doubling the active layer thickness or using an alternative ruthenium dye, but a metal-free donor-π-acceptor dye exhibited a much smaller decrease in current due to its higher excited state energy. We develop a model employing prior research on Al(2)O(3) growth and dye kinetics that successfully predicts the reduction in device current as a function of ALD cycles and is extendable to different dye-barrier systems.     

Effect of the rutile content on the photovoltaic performance of the dye-sensitized solar cells composed of mixed-phase TiO2 photoelectrodes

The effect of the rutile content on the photovoltaic performance of dye-sensitized solar cells (DSSCs) composed of mixed-phase TiO(2) photoelectrode has been investigated. The mixed-phase TiO(2) particles with varied amounts of rutile, relative to anatase phase, are synthesized by an in situ method where the concentration of sulfate ion is used as a phase-controlling parameter in the formation of TiO(2) using TiCl(4) hydrolysis. The surface area (S(BET)) varies from 33 (pure rutile) to 165 (pure anatase) m(2) g(-1). Generally, both the current density (J(sc)) and photo-conversion efficiency (η) decrease as the rutile content increases. The incorporation of rod-shaped rutile particles causes low uptake of dye due to the reduced surface area, as well as slow electron transport in less efficiently-stacked structure. However, maximum J(sc) (14.63 mA cm(-2)) and η (8.69%) appear when relatively low rutile content (16%) is employed. The reported synergistic effect by the efficient interparticle electron transport from rutile to anatase seems to overbalance the decrease of surface area when small amount of rutile particles is incorporated.     

Facile synthesis of TiO2 inverse opal electrodes for dye-sensitized solar cells

Engineering of TiO(2) electrode layers is critical to guaranteeing the photoconversion efficiency of dye-sensitized solar cells (DSSCs). Recently, a novel approach has been introduced for producing TiO(2) electrodes using the inverted structures of colloidal crystals. This paper describes a facile route to producing ordered macroporous electrodes from colloidal crystal templates for DSSCs. Using concentrated colloids dispersed in a volatile medium, the colloidal crystal templates were obtained within a few minutes, and the thickness of the template was easily controlled by changing the quantity of colloidal solution deposited. Here, the effects of the structural properties of the inverse opal TiO(2) electrodes on the photovoltaic parameters of DSSCs were investigated. The photovoltaic parameters were measured as a function of pore ordering and electrode film thickness. Moreover, DSSC applications that used either liquid or viscous polymer electrolyte solutions were investigated to reveal the effects of pore size on performance of an inverse opal TiO(2) electrode.     

An efficient 3C-silicon carbide/titania nanocomposite photoelectrode for dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs) are fabricated using a novel 3C-SiC/TiO(2) nanocomposite as a photoelectrode to enhance the power conversion efficiency. Compared with a pristine nanocrystalline TiO(2) cell, a DSSC based on a 3C-SiC (0.04 wt%)/TiO(2) nanocomposite photoelectrode shows ~115% increase in power conversion efficiency.     

Y3Al5O12:Ce phosphors as a scattering layer for high-efficiency dye sensitized solar cells

Y(3)Al(5)O(12):Ce phosphors have been prepared and used as an effective scattering layer on top of a transparent layer of nanocrystalline TiO(2) for dye sensitized solar cells (DSSCs). The Y(3)Al(5)O(12):Ce scattering layer increases the photocurrent of DSSCs due to the enhanced light harvesting mainly via the improved light absorption and scattering. Under one sun illumination (AM 1.5G, 100 mW cm(-2)), a high efficiency of 7.91% was achieved for the cell with a Y(3)Al(5)O(12):Ce scattering layer, which is an increase of 13.5% compared to the cell without a scattering layer (6.97%).     

Sea urchin TiO2-nanoparticle hybrid composite photoelectrodes for CdS/CdSe/ZnS quantum-dot-sensitized solar cells

The sea urchin TiO(2) (SU TiO(2)) particles composed of radially aligned rutile TiO(2) nanowires are successfully synthesized through the simple solvothermal process. SU TiO(2) was incorporated into the TiO(2) nanoparticle (NP) network to construct the SU-NP composite film, and applied to the CdS/CdSe/ZnS quantum-dot-sensitized solar cells (QDSSCs). A conversion efficiency of 4.2% was achieved with a short-circuit photocurrent density of 18.2 mA cm(-2) and an open-circuit voltage of 531 mV, which corresponds to ～20% improvement as compared with the values obtained from the reference cell made of the NP film. We attribute this extraordinary result to the light scattering effect and efficient charge collection.     

Theoretical investigation of triphenylamine dye/titanium dioxide interface for dye-sensitized solar cells

The structural, electronic and optical features of two metal-free triphenylamine (TPA) organic dyes (namely C206 and C217) before and after binding to a TiO(2) anatase nanoparticle have been investigated in detail, as a model for the corresponding dye-sensitized solar cells (DSSCs). The combination of density functional tight-binding (DFTB), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches are employed. To understand the effects of the linker part in the TPA organic dyes on the energy conversion efficiency of the DSSCs, C217 and C206, which share the same donor and anchor parts but different linker parts, are theoretically evaluated. Our results show that compared with C206 containing just one thienothiophene unit as the linker, for C217 the introduction of one electron-rich 3,4-ethylenedioxythiophene group to the linker part results in stronger couplings with the TiO(2) conduction band and more efficient electron transfer. This difference contributes to the higher efficiency of C217 in DSSCs experiments. This study is expected to assist the molecular design of new and more efficient TPA-based organic dyes for the optimization of the DSSCs.     

Influence of surface-attachment functionality on the aggregation, persistence, and electron-transfer reactivity of chalcogenorhodamine dyes on TiO2

Chalcogenorhodamine dyes bearing phosphonic acids and carboxylic acids were compared as sensitizers of nanocrystalline TiO(2) in dye-sensitized solar cells (DSSCs). The dyes were constructed around a 3,6-bis(dimethylamino)chalcogenoxanthylium core and varied in the 9 substituent: 5-carboxythien-2-yl in dyes 1-E (E = O, Se), 4-carboxyphenyl in dyes 2-E (E = O, S), 5-phosphonothien-2-yl in dyes 3-E (E = O, Se), and 4-phosphonophenyl in dyes 4-E (E = O, Se). All dyes adsorbed to TiO(2) as mixtures of H aggregates and monomers, which exhibited broadened absorption spectra relative to those of purely amorphous monolayers. Surface coverages of dyes and the extent of H aggregation varied minimally with the surface-attachment functionality, the structure of the 9-aryl group, and the identity of the chalcogen heteroatom. Carboxylic acid-functionalized dyes 1-E and 2-E desorbed rapidly and completely from TiO(2) into acidified CH(3)CN, but phosphonic acid-functionalized dyes 3-E and 4-E persisted on TiO(2) for days. Short-circuit photocurrent action spectra of DSSCs corresponded closely to the absorptance spectra of dye-functionalized films; thus, H aggregation did not decrease the electron-injection yield or charge-collection efficiency. Maximum monochromatic incident photon-to-current efficiencies (IPCEs) of DSSCs ranged from 53 to 95% and were slightly higher for carboxylic acid-functionalized dyes 1-E and 2-E. Power-conversion efficiencies of DSSCs under white-light illumination were low (<1%), suggesting that dye regeneration was inefficient at high light intensities. The photoelectrochemical performance (under monochromatic or white-light illumination) of 1-E and 2-E decayed significantly within 20-80 min of the assembly of DSSCs, primarily because of the desorption of the dyes. In contrast, the performance of phosphonic acid-functionalized dyes remained stable or improved slightly on similar timescales. Thus, replacing carboxylic acids with phosphonic acids increased the inertness of chalcogenorhodamine-TiO(2) interfaces without greatly impacting the aggregation of dyes or the interfacial electron-transfer reactivity.     

TiO2纳米粒子膜的制备、表面态性质和光催化活性

在酸性和碱性条件下,用TiCl4水解法制备了TiO2纳米粒子膜催化剂.采用原子力显微镜(AFM),X射线衍射(XRD),表面光电压谱(SPS)和场诱导表面光电压谱(EFISPS)测定了催化剂表面的微结构及能级结构.对催化剂进行了光催化降解苯酚实验,测定了其光催化活性.结果表明,酸性条件下制备的TiO2膜催化剂的光催化活性较高,其结果接近于P25.用能带理论解释了TiO2纳米粒子膜催化剂光催化活性的差异,分析了膜厚对光催化活性的影响.