Gentian Yue

A highly efficient flexible dye-sensitized solar cell based on nickel sulfide/platinum/titanium counter electrode

A composite film of nickel sulfide/platinum/titanium foil (NiS/Pt/Ti) with low cost and high electrocatalytic activity was synthesized by the use of an in situ electropolymerization route and proposed as a counter electrode (CE) catalyst for flexible dye-sensitized solar cells (FDSSCs). The FDSSC with the NiS/Pt/Ti CE exhibited a comparable power conversion efficiency of 7.20% to the FDSSC with the platinum/titanium (Pt/Ti) CE showing 6.07%. The surface morphology of the NiS/Pt/Ti CE with one-dimensional (1D) structure is characterized by using the scanning electron microscopy (SEM). The NiS/Pt/Ti CE also displayed multiple electrochemical functions of excellent conductivity, great electrocatalytic ability for iodine/triiodine, and low charge transfer resistance of 2.61 ± 0.02 Ω cm2, which were characterized by using the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization plots. The photocurrent-photovoltage (J-V) character curves were further used to calculate the theoretical optical light performance parameters of the FDSSCs. It may be said that the NiS/Pt/Ti counter electrode is a promising catalytic material to replace the expensive platinum in FDSSCs.

Pulse electropolymerization of high performance PEDOT/MWCNT counter electrodes for Pt-free dye-sensitized solar cells

High performance poly(3,4-ethylenedioxythiophene) (PEDOT) nano-meadows were electropolymerized onto multi-wall carbon nanotube (MWCNT) as counter electrodes (CEs) for Pt-free dye-sensitized solar cells (DSCs) for the first time. This composite film was fabricated using an electrophoresis of MWCNTs onto a fluorinated tin oxide glass substrate and then subjected to PEDOT electropolymerization by using the pulse potentiostatic method. The surface of MWCNTs was wrapped with nano-meadows PEDOT thin film of ∼55 nm in thickness. The extensive cyclic voltammograms (CV) showed PEDOT/MWCNT CE with excellent electrocatalytic activity for I3− reduction. Moreover, the peak current densities of the PEDOT/MWCNT CE showed no sign of degradation after consecutive 200 CV tests, suggesting the great electrochemical stability of the PEDOT/MWCNT CE. The electrochemical impedance spectroscopy demonstrated that the PEDOT/MWCNT CE had the lowest charge-transfer resistance among all CEs tested in this study. The DSC assembled with the PEDOT/MWCNT composite CE demonstrated an enhanced photovoltaic conversion efficiency of 7.03% compared to that using conventional Pt CE (5.88%) under full sunlight illumination (100 mW cm−2, AM1.5 G) due to the intrinsic superior electrocatalytic activity of the nano-meadows PEDOT material, highly specific surface area and high electrical conductivity of the MWCNTs. Therefore, the PEDOT/MWCNT CE can be considered as a promising alternative CE for use in Pt-free DSCs.

A large-area light-weight dye-sensitized solar cell based on all titanium substrates with an efficiency of 6.69% outdoors.

Light-weight PEDOT-Pt/Ti mesh and Ti/TiO(2) foil electrodes are prepared. Owing to the PEDOT-Pt/Ti photocathodes high transparency, good electrocatalytic activity, and low resistance; the Ti/TiO(2) anodes large specific area and high conductivity, a light-weight backside illuminated large-area (100 cm(2) ) dye-sensitized solar cell achieves an energy conversion efficiency of 6.69% under an outdoors sunlight irradiation of 55 mW cm(-2) .

High performance platinum-free counter electrode of molybdenum sulfide–carbon used in dye-sensitized solar cells

A high porous molybdenum sulfide–carbon (MoS2–C) hybrid film was prepared by using an in situ hydrothermal route. The MoS2–C hybrid film served as a low-cost and high efficient platinum-free counter electrode for a dye-sensitized solar cell (DSSC). The cyclic voltammetry, electrochemical impedance spectroscopy and Tafel curve analysis indicate that the MoS2–C electrode possesses low charge transfer resistance on the electrolyte–electrode interface, high electrocatalytic activity and fast reaction kinetics for the reduction of triiodide to iodide at the counter electrode, which is due to large specific surface area and special structure and compositions of MoS2–C film. A DSSC with the novel MoS2–C counter electrode achieve a high power conversion efficiency of 7.69% under standard light illumination, which exceeds that of the DSSC with a Pt counter electrode (6.74%).

Bifacial dye-sensitized solar cells: A strategy to enhance overall efficiency based on transparent polyaniline electrode

Dye-sensitized solar cell (DSSC) is a promising solution to global energy and environmental problems because of its clean, low-cost, high efficiency, good durability, and easy fabrication. However, enhancing the efficiency of the DSSC still is an important issue. Here we devise a bifacial DSSC based on a transparent polyaniline (PANI) counter electrode (CE). Owing to the sunlight irradiation simultaneously from the front and the rear sides, more dye molecules are excited and more carriers are generated, which results in the enhancement of short-circuit current density and therefore overall conversion efficiency. The photoelectric properties of PANI can be improved by modifying with 4-aminothiophenol (4-ATP). The bifacial DSSC with 4-ATP/PANI CE achieves a light-to-electric energy conversion efficiency of 8.35%, which is increased by ~24.6% compared to the DSSC irradiated from the front only. This new concept along with promising results provides a new approach for enhancing the photovoltaic performances of solar cells.

Pulse electrodeposition of CoS on MWCNT/Ti as a high performance counter electrode for a Pt-free dye-sensitized solar cell

Because of the large specific surface area and superior electrical conductivity of multi-wall carbon nanotubes (MWCNTs) and the high electrocatalytic activity of cobalt sulfide (CoS), CoS/MWCNT hybrid films are deposited onto Ti foil substrates by sequential electrophoresis and pulse potentiostatic electrodeposition. Field-emission scanning electron microscopy observes that the surface of the MWCNTs is wrapped with a nano-honeycomb CoS thin film of ∼55 nm in thickness. Cyclic voltammograms, electrochemical impedance spectroscopy, and Tafel polarization characterization indicate that the CoS/MWCNT/Ti counter electrode (CE) has better electrocatalytic activity for I3− reduction than Pt CE. Under full sunlight illumination (100 mW cm−2, AM 1.5 G), the dye-sensitized solar cell based on the CoS/MWCNT/Ti CE achieves a power conversion efficiency of 8.05%, which exceeds that of the device based on Pt/Ti CE (6.39%).

A high performance Pt-free counter electrode of nickel sulfide/multi-wall carbon nanotube/titanium used in dye-sensitized solar cells

Multi-wall carbon nanotubes (MWCNTs) were deposited on a titanium (Ti) foil substrate by using electrophoresis, then a nano-corallines nickel sulfide (NiS) was deposited on the MWCNTs by using a pulse potentiostatic method. The high performance NiS/MWCNT/Ti hybrid film was firstly used as a Pt-free counter electrode (CE) in dye-sensitized solar cells (DSSCs). The surface of MWCNTs was wrapped with a nano-corallines NiS thin film of ∼45 nm in thickness. Under full sunlight illumination (100 mW cm−2, AM 1.5 G), DSSCs with a NiS/MWCNT/Ti CE achieved an enhanced photovoltaic conversion efficiency of 7.90%, while DSSCs with a Pt/Ti CE obtained the efficiency of 6.36%. The characterization of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated that nano-corallines NiS had high electrocatalytic activity for I3− reduction, MWCNTs had high specific surface area and low resistance, and the synergistic effect of NiS and MWCNTs endowed the superior features of the hybrid film. Therefore, the NiS/MWCNT/Ti CE can be used as a promising alternative CE in low-cost and large-scale DSSCs.

Dual functions of YF3:Eu3+ for improving photovoltaic performance of dye-sensitized solar cells

In order to enhance the photovoltaic performance of dye-sensitized solar cell (DSSC), a novel design is demonstrated by introducing rare-earth compound europium ion doped yttrium fluoride (YF3:Eu3+) in TiO2 film in the DSSC. As a conversion luminescence medium, YF3:Eu3+ transfers ultraviolet light to visible light via down-conversion, and increases incident harvest and photocurrent of DSSC. As a p-type dopant, Eu3+ elevates the Fermi level of TiO2 film and thus heightens photovoltage of the DSSC. The conversion luminescence and p-type doping effect are demonstrated by photoluminescence spectra and Mott-Schottky plots. When the ratio of YF3:Eu3+/TiO2 in the doping layer is optimized as 5 wt.%, the light-to-electric energy conversion efficiency of the DSSC reaches 7.74%, which is increased by 32% compared to that of the DSSC without YF3:Eu3+ doping. Double functions of doped rare-earth compound provide a new route for enhancing the photovoltaic performance of solar cells.

Application of Y2O3:Er3+ Nanorods in Dye‐Sensitized Solar Cells

Y(2)O(3):Er(3+) nanorods are synthesized by means of a hydrothermal method and then introduced into a TiO(2) electrode in a dye-sensitized solar cell (DSSC). Y(2)O(3):Er(3+) improves infrared light harvest via up-conversion luminescence and increases the photocurrent of the DSSC. The rare earth ions improve the energy level of the TiO(2) electrode through a doping effect and thus increase the photovoltage. The light scattering is ameliorated by the one-dimensional nanorod structure. The DSSC containing Y(2)O(3):Er(3+) (5 wt%) in the doping layer achieves a light-to-electric energy conversion efficiency of 7.0%, which is an increase of 19.9% compared to the DSSC lacking of Y(2)O(3):Er(3+).

Glucose aided preparation of tungsten sulfide/multi-wall carbon nanotube hybrid and use as counter electrode in dye-sensitized solar cells.

The tungsten sulfide/multi-wall carbon nanotube (WS(2)/MWCNT) hybrid was prepared in the presence of glucose by the hydrothermal route. The hybrid materials were used as counter electrode in the dye-sensitized solar cell (DSSC). The results of cyclic voltammetry measurement and electrochemical impedance spectroscopy indicated that the glucose aided prepared (G-A) WS(2)/MWCNT electrode had low charge-transfer resistance (R(ct)) and high electrocatalytic activity for triiodide reduction. The excellent electrochemical properties for (G-A) WS(2)/MWCNT electrode is due to the synergistic effects of WS(2) and MWCNTs, as well as amorphous carbon introduced by glucose. The DSSC based on the G-A WS(2)/MWCNT counter electrode achieved a high power conversion efficiency of 7.36%, which is comparable with the performance of the DSSC using Pt counter electrode (7.54%).