Fiber-shaped Dye-sensitized Solar Cells Research Articles

One step hydrothermal synthesis of vertical Ni-Mo-S nanosheet array as the counter electrode for FDSC

In order to further improve electrocatalytic ability of MoS2 counter electrode(CE) in fiber-shaped dye sensitized solar cells(FDSSCs), Ni element was introduced and Ni-Mo-S nanosheet array was prepared by a simple one-step hydrothermal process. By utilizing synergetic effects between two transition metals and more catalytically active edges in Ni-Mo-S nanosheet array, lower series transfer resistance(Rct) at the interface of CE/electrolyte in the electrochemical impedance spectra (EIS) measurement and higher cathodic peak current in the cyclic voltammetry (CV) measurement were obtained when compared with MoS2, indicating Ni-Mo-S processed superior electrocatalytic activity to MoS2. As a result, power conversion efficiency of Ni-Mo-S based FDSSC(6.3%) was found to be higher than MoS2-based FDSSC (4.2%), comparable to Pt based FDSSC(6.4%).

Hierarchically structured photoanode with enhanced charge collection and light harvesting abilities for fiber-shaped dye-sensitized solar cells

The performances of fiber dye-sensitized solar cells (FDSSCs), in terms of charge collection efficiency, light-harvesting ability, and structural stability, are improved through a novel hierarchically structured photoanode based on a Ti microridge/nanorod-modified wire substrate. The microridge made of several Ti micropits is inserted into TiO2 layer to shorten the photoelectron transport distance from the original place in the TiO2 layer to substrate and to increase the electron transport rate. The Ti micropits are used as light-gathering centers to collect the reflected light. Meanwhile, the Ti nanorods are evenly distributed on the surface of the microridge-coated Ti wire substrate, which increases the contact area between the substrate and the TiO2 layer in order to suppress the electron recombination and scatters the incident light to further improve the light-harvesting ability. Therefore, the charge collection and power conversion efficiencies of the novel FDSSC have been accordingly enhanced by 17.7% and 61.6%, respectively, compared with traditional FDSSC. Moreover, the structural stability of the novel FDSSC has been strengthened.

(Invited) Energy Harvesting and Storage in 1D Devices

It is critically important to develop miniature energy storage and conversion devices in modern electronics, e.g., for portable and wearable electronic facilities. Here a novel family of energy storage and conversion devices as well as their integrated devices in 1D configuration are carefully discussed with unique and promising advantages such as lightweight and weaveable compared with the conventional planar architecture. For the energy conversion devices in 1D configuration, fiber-shaped dye-sensitized solar cells, polymer solar cells and perovskite solar cells are covered. For the energy storage devices, fiber-shaped electrochemical capacitors, lithium ion batteries, lithium sulfur batteries, lithium air batteries and zinc air batteries are carefully investigated. The main efforts will be made to highlight the recent advancement in the electrode material, device structure and property extension.

Study on a stretchable, fiber-shaped, and TiO2 nanowire array-based dye-sensitized solar cell with electrochemical impedance spectroscopy method

A spring-like Ti@TiO2 nanowire array wire has been introduced into a stretchable fiber-shaped dye-sensitized solar cell (FDSSC) as a photoanode to achieve high flexibility and elasticity in this paper. Given the TiO2 layer, which was prepared by a hydrothermal reaction in the optimized NaOH concentration of 2.5 mol L−1, with a 1D structure and high adhesion between the TiO2 nanowire array and the Ti wire substrate, the novel FDSSC still possesses photoelectric conversion efficiency retention rates of approximately 97.00% and 95.95% after bending to a radius of 1.0 cm and stretching to 100% strain, respectively. EIS result shows the degradation mechanism of the FDSSC photoelectric performance: the bending test leads to more terrible electron combination; the stretching operation increases the internal resistance and charge-transfer resistance at the counter electrode. Moreover, it's worth noting that, this is the first time to show a 100%-stretching degree in the FDSSC research field so far.

A fiber-shaped solar cell showing a record power conversion efficiency of 10%

Hydrophobic core/hydrophilic sheath fibers have been designed for fiber-shaped dye-sensitized solar cells showing a record power conversion efficiency of 10%.

NiCo2S4 nanosheets in situ grown on carbon fibers as an efficient counter electrode for fiber-shaped dye-sensitized solar cells

NiCo2S4 nanosheets were successfully in situ grown on carbon fibers via one-step process and used in fiber-shaped dye sensitized solar cells (FDSSCs) as counter electrodes (CEs). The electrocatalytic ability and electrochemical properties of the NiCo2S4-CF CE were studied by cyclic voltammetry and electrochemical impedance spectroscopy. The power conversion efficiency of 6.31% was achieved by the FDSSC based on NiCo2S4-CF CE, which is superior to that of the device using Pt wire CE (6.03%).

Research progress on fiber-shaped dye-sensitized solar cells

As the increasingly serious problems of fossil energy depletion and environmental pollutions, exploiting the clean renewable energy resources has become the urgency. Solar energy is one of the important renewable energy resources, and its effective utilization will exert a great influence on solving energy and environmental problems. Solar cells, which convert solar energy to electrical energy, represent a promising candidate to use renewable energies. In the past 20 years, the dye-sensitized solar cells (DSSCs) have drawn much attention from both academia and industry due to its low cost, environment-friendliness and high efficiency. It was reported that the efficiency of traditional DSSCs using fluorine- doped tin oxide (FTO) glass as the working electrode substrate exceeded 12% (100 mW/cm2). But rigid flat-shaped DSSCs are unfavorable for installation, transportation, and application as a result of their extreme brittleness and heaviness. Therefore, the development of flexible cells has become a challenge. Fiber-shaped dye-sensitized solar cells (F-DSSCs) are flexible DSSCs that fabricated by assembling the photovoltaic function on the surface of fiber-shaped conductive substrate with high curvature structure. The fiber cells show unique and promising advantages: (1) Since they have a three-dimensional structure and very low dependence on incident light angle, they can catch more photons from all directions and gather diffused/reflected light to improve the power output of the cell. (2) The fiber cell has smaller package area ratio. A larger area cell can be assembled by simply increasing the length of the cell. The characteristic of F-DSSCs is that when the cells go up to some extent, the package area of the cell remains basically unchanged, which has a great significance in maintaining the stability of F-DSSCs with larger size. (3) F-DSSCs can directly adopt traditional preparation technology, even under milder processing conditions, such as low temperature. (4) F-DSSCs are lightweight so that they are easy to be woven into clothes or integrated into other structures by existing textile techniques, which enables applications in electronic textiles and various complex devices. Therefore, extensive attention has recently been paid to develop F-DSSCs photovoltaic devices, and the maximum energy conversion efficiencies have exceeded 8%. However, a few critical scientific issues still need to be addressed. Firstly, it is necessary to make further and deeper research on solid-state electrolytes to improve the stability of F-DSSCs. Secondly, more efforts are required to explore new photoactive materials and electrodes. Meanwhile, optimizing the F-DSSCs structures and developing the scale-up technologies will enhance the conversion efficiencies which are currently much lower than traditional planar DSSCs counterparts. Thirdly, F-DSSCs may be integrated with other energy storage parts to produce more efficient devices. To accomplish this, much more efforts should be made to optimize the structure and improve the performance of the integrated fiber. In this review, the basic structure and working principle of F-DSSCs are briefly introduced. The related researches in recent years are reviewed in detail, including working electrodes, counter electrodes and electrolytes. At the same time, future development trends are forecasted.

Self-powered textile for wearable electronics by hybridizing fiber-shaped nanogenerators, solar cells, and supercapacitors.

Wearable electronics fabricated on lightweight and flexible substrate are believed to have great potential for portable devices, but their applications are limited by the life span of their batteries. We propose a hybridized self-charging power textile system with the aim of simultaneously collecting outdoor sunshine and random body motion energies and then storing them in an energy storage unit. Both of the harvested energies can be easily converted into electricity by using fiber-shaped dye-sensitized solar cells (for solar energy) and fiber-shaped triboelectric nanogenerators (for random body motion energy) and then further stored as chemical energy in fiber-shaped supercapacitors. Because of the all-fiber-shaped structure of the entire system, our proposed hybridized self-charging textile system can be easily woven into electronic textiles to fabricate smart clothes to sustainably operate mobile or wearable electronics.

Electrophoretic deposition of graphene-TiO2 hierarchical spheres onto Ti thread for flexible fiber-shaped dye-sensitized solar cells

A multiple electrophoretic deposition (EPD) technique is developed to deposit complicated hierarchical TiO2 spheres and graphene-TiO2 spheres composite onto flexible Ti thread as working electrode of fiber-shaped dye-sensitized solar cells (F-DSSCs). Experimental results show that this multiple EPD technique cannot only fill up the cracks coming from drying the previous single EPD film but also adjust the thickness of films. More importantly, this approach is adaptable to build both single material and more complicated composite on the fiber-shaped substrates. With this technique, high quality graphene-TiO2 film is acquired on flexible Ti thread and F-DSSCs based on 0.3wt.% graphene-TiO2 hierarchical spheres show a remarkable enhancement in conversion efficiency (2.68%) compared to that of bare TiO2 hierarchical spheres (1.50%). Further TiCl4 solution treatment of 0.3wt.% graphene-TiO2 photoanode achieves device efficiency of 3.26% resulting from the improved connectivity between the particles in the film. Our work may establish an industrial procedure to produce complex hierarchical architecture on the high curvature surface of the flexible substrates with broader range of practical application.

In situ direct growth of single crystalline metal (Co, Ni) selenium nanosheets on metal fibers as counter electrodes toward low-cost, high-performance fiber-shaped dye-sensitized solar cells.

Highly crystalline metal (Co, Ni) selenium (Co0.85Se or Ni0.85Se) nanosheets were in situ grown on metal (Co, Ni) fibers (M-M0.85Se). Both M-M0.85Se (Co-Co0.85Se and Ni-Ni0.85Se) fibers prove to function as excellent, low-cost counter electrodes (CEs) in fiber-shaped dye-sensitized solar cells (FDSSCs) with high power conversion efficiency (Co-Co0.85Se 6.55% and Ni-Ni0.85Se 7.07%), comparable or even superior to a Pt fiber CE (6.54%). The good performance of the present Pt-free CE-based solar cell was believed to originate from: (1) the intrinsic electrocatalytic properties of the single-crystalline M-M0.85Se; (2) the enough void space among M0.85Se nanosheets that allows easier redox ion diffusion; (3) the two-dimensional morphology that provides a large contact area between the CE catalytic material and electrolyte; (4) in situ direct growth of the M0.85Se on metal fibers that renders good electrical contact between the active material and the electron collector.

Improving the photovoltaic performance and flexibility of fiber-shaped dye-sensitized solar cells with atomic layer deposition

A conformal and thin TiO2 film fabricated with atomic layer deposition (ALD) improves the performance of fiber-shaped dye-sensitized solar cells (FDSSCs). Electrical contact at Ti/TiO2 is improved through insertion of a uniform and pinhole-free TiO2 film. The film thickness varies from 5nm to 40nm, and the high power conversion efficiency of 7.41% is achieved from a typical device with a 15nm TiO2 film and a 10μm TiO2 nanoparticles layer. The compact and high-quality TiO2 film improves Ti/TiO2 interfacial property. Surface modification hastens electron transport, which thus improves the charge collection efficiency. Both photocurrent density and bending performance are significantly enhanced compared with those of the corresponding FDSSCs without ALD treatment.

Macroscopic Graphene Fibers Directly Assembled from CVD-Grown Fiber-Shaped Hollow Graphene Tubes.

Using a copper wire as the substrate for the CVD growth of a hollow multilayer graphene tube, we prepared a macroscopic porous graphene fiber by removing the copper in an aqueous mixture solution of iron chloride (FeCl3, 1 M) and hydrochloric acid (HCl, 3 M) and continuously drawing the newly released graphene tube out of the liquid. The length of the macroscopic graphene fiber thus produced is determined mainly by the length of the copper wire used. The resultant macroscopic graphene fiber with the integrated graphene structure exhibited a high electrical conductivity (127.3 S cm(-1)) and good flexibility over thousands bending cycles, showing great promise as flexible electrodes for wearable optoelectronics and energy devices-exemplified by its use as a flexible conductive wire for lighting a LED and a cathode in a fiber-shaped dye-sensitized solar cell (DSSC) with one of the highest energy conversion efficiencies (3.25%) among fiber-shaped DSSCs.

Synthesis and photovoltaic application of platinum-modified conducting aligned nanotube fiber

Platinum-modified carbon nanotube (CNT) fibers with controlled platinum weight percentages were synthesized via an electrochemical deposition method. Platinum nanoparticles can be uniformly deposited on the surface of the aligned CNTs in the fiber, which possesses an efficient improved catalytic activity in the reduction of I3 −/I− compared with other fiber materials such as a carbon fiber without the aligned nanostructure. The hybrid CNT fiber was further used as a counter electrode to fabricate fiber-shaped dye-sensitized solar cell (DSSC). A maximal power conversion efficiency of 8.10% was achieved, compared with that of 4.91% for a bare aligned CNT fiber and 5.50% for a platinum-modified carbon fiber as the counter electrode under the same condition.

Controllable electrophoresis deposition of TiO2 mesoporous spheres onto Ti threads as photoanodes for fiber-shaped dye-sensitized solar cells

The electrophoresis deposition technique was applied to fabricate fiber-shaped dye-sensitized solar cells (FDSSC) by depositing TiO2 mesoporous sphere onto a Ti wire as a photoanode. The total conversion efficiency of the FDSSC achieves 3.8%.

One-step growth of CoNi2S4 nanoribbons on carbon fibers as platinum-free counter electrodes for fiber-shaped dye-sensitized solar cells with high performance: Polymorph-dependent conversion efficiency

Both the CoNi2S4 nanoribbon on carbon fibers (CoNi2S4 nanoribbon-CF) and CoNi2S4 nanorod on carbon fibers (CoNi2S4 nanorod-CF) were fabricated as counter electrodes (CEs) for fiber-shaped dye-sensitized solar cells (FDSSCs). The CoNi2S4 nanorod-CF-based FDSSC with high conversion efficiency of 7.03%, comparable or even superior to Pt wire CE (6.45%). However, the CoNi2S4 nanorod-CF-based counterpart with conversion efficiency of 4.10%, demonstrates that the high conversion efficiency of the CoNi2S4 nanoribbon-CF-based FDSSC is not only strongly dependent on the intrinsic properties of the selected CE species, but also closely related to their polymorph structure. The different exposed crystal facet is suggested responsible for the significant distinction of conversion efficiency between two one-dimensional CoNi2S4 nanostructures. This work also gives some clues to the future development and rational design of ternary nickel–cobalt chalcogens potentially used in fiber-shaped fuel cells or supercapacitors.

Porous, single crystalline titanium nitride nanoplates grown on carbon fibers: excellent counter electrodes for low-cost, high performance, fiber-shaped dye-sensitized solar cells.

An excellent, platinum free fiber counter electrode (CE) was successfully fabricated, consisting of porous, single crystalline titanium nitride (TiN) nanoplates grown on carbon fibers (CF). The fiber-shaped dye-sensitized solar cells (FDSSCs) based on the TiN-CF CE show a high conversion efficiency of 7.20%, comparable or even superior to that of the Pt wire (6.23%).

Quasi-solid-state, coaxial, fiber-shaped dye-sensitized solar cells

A quasi-solid-state, coaxial, fiber-shaped dye-sensitized solar cell is developed by wrapping transparent and conducting carbon nanotube sheets on a modified Ti wire. The use of eutectic melts and design of the coaxial structure enable effective contacts between the two electrodes and active layer with a good performance, including high thermal stability and flexibility.

Wet-process preparation of nickel-based photoanode for TCO-less fiber-shaped dye-sensitized solar cells

Low-cost ZnO-type fiber-shaped dye-sensitized solar cells (DSSC) without transparent conductive oxide (TCO) were for the first time assembled through a low-temperature all-wet process, using a series of Ni-based composite fiber. Both Ni layer morphology and ZnO nano-array structure evidently influenced the performance of the corresponding DSSC. For applications in both liquid type and all-solid CuI type fiber-shaped DSSCs, the Ni-based photoanode is comparable with the Ti- or Fe-based photoanode. Our all-solid CuI type fiber-shaped DSSCs was even better than that of the reported all-solid Ti- or Fe-based devices with the same oxide thickness. Electrochemical analysis further indicated that side reactions on the electrode/electrolyte interface could be effectively suppressed after a layer of Ni plated. Even for Cu wire, of which its interfacial side reactions are too complicated for application in DSSC, the Cu/Ni composite fiber still works well. Similar technology can be used to fabricate many other low-cost and light-weight conductive fibers, which are potential photoanode materials for highly efficient TCO-less DSSCs.

Facial synthesis of SnO2 nanoparticle film for efficient fiber-shaped dye-sensitized solar cells

SnO2 nanoparticle film is directly prepared by in situ thermal calcining isopropanol solution of tin tetraisopropoxide, and is used to construct the SnO2–TiO2 junction on titanium wire substrate. The titanium wire supported SnO2–TiO2 junction is further applied to fiber-shaped dye-sensitized solar cells (FDSCs). High efficiency of 5.8% (Normal Model) and 12.4% (Diffuse Model) are achieved. Our results indicate that Jsc enhancement derived by SnO2–TiO2 junction and the recombination shielding effect of the compact TiO2 film could synergistically contribute to high efficiencies. This study offers a novel and alternative strategy for achieving efficient SnO2–TiO2 junction based solar cells in a facile, scalable and cost-effective way.

The spray pyrolysis of alkoxide sols on the electrode of fiber-shaped solar cells

This work investigated the flow-field structure of the aerosol when spray pyrolyzing alkoxide sols on the anode of fiber-shaped dye sensitized solar cell. The re-atomization of alkoxide sols was optimized via computational fluid dynamics simulation and validated by experimental observation to provide aerosol flow with higher uniformity. The interaction between the fiber substrates and the aerosol flow was also studied. Different from that on the traditional plate substrate, two flow patterns would be generated, including the flow split in two flanks along the axial direction and the flow around the cylindrical surface. The interference of different flows would result periodical convergences of streamlines. With the assistant of the flow around the cylindrical surface, necklace-like sol drops would then accumulated along the fibers, which is also related with the surface tension. Fiber-shaped photo-anode with different micro structures of TiO2 films have been prepared from different type of aerosol flows and applied in fiber-shaped dye-sensitized solar cell. To improve the performance, the re-atomization should be further enhanced and the convergence of streamlines should be avoided. The mechanism of spray pyrolysis on fiber is evidently different from that on plate substrates.