Jihuai Wu

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.

An All-Solid-State Dye-Sensitized Solar Cell-Based Poly(N-alkyl-4-vinyl-pyridine iodide) Electrolyte with Efficiency of 5.64%

Using poly(N-methyl-4-vinyl-pyridine iodide), N-methyl-pyridine iodide and iodine, a solid polymer electrolyte with conductivity of 6.41 mS/cm is prepared. On the basis of a solid polymer electrolyte, a conducting graphite layer, a KI block layer, and a vacuum assembling technique, we achieve an all-solid-state dye-sensitized solar cell with total photoelectric conversion efficiency of 5.64% under AM 1.5 simulated solar light (100 mW/cm2) illumination.

Progress on the electrolytes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have aroused intense interest over the past decade owing to their low cost and simple preparation procedures. Much effort has been devoted to the study of electrolytes that enable light-to-electrical power conversion for DSSC applications. This review focuses on recent progress in the field of liquid, solid-state, and quasi-solid-state electrolytes for DSSCs. It is believed that quasi-solid-state electrolytes, especially those utilizing thermosetting gels, are particularly applicable for fabricating high photoelectric performance and long-term stability of DSSCs in practical applications.

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.

A simple and high-effective electrolyte mediated with p-phenylenediamine for supercapacitor

A redox intermedium p-phenylenediamine (PPD) with quick reversible faradaic processes is introduced into KOH electrolyte, referred to as pseudocapacitive effect occurring on the electrode/electrolyte surface. The KOH + PPD electrolyte as potential electrolyte for supercapacitors is investigated by UV-Vis spectroscopy and electrochemical methods. As expected, the supercapacitor with KOH + PPD electrolyte has a much higher electrode specific capacitance (605.225 F g−1) than the one with conventional KOH electrolyte (144.037 F g−1) at the same current density of 1 A g−1. Simultaneously, the supercapacitor with KOH + PPD electrolyte exhibits a much higher energy density (19.862 W h kg−1) than the supercapacitor with conventional KOH electrolyte (4.458 W h kg−1). Furthermore, the supercapacitor with KOH + PPD electrolyte shows superior charge–discharge stability. After 4000 cycles, its capacitive retention ratio is still as high as 94.530%.

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%).

Conducting film from graphite oxide nanoplatelets and poly(acrylic acid) by layer-by-layer self-assembly

A [poly(acrylic acid)/graphite oxide]n [(PAA/GO)(n)] film with a conductivity of 60 S.cm(-1) was grown layer-by-layer (LbL) using Langmuir-Blodgett self-assembly techniques. GO nanoplatelets were prepared from natural graphite by oxidizing, ball milling, exfoliating, and modifying with cationic surfactant cetyltrimethylammonium bromide (CTAB). The X-ray diffraction pattern reveals that PAA and GO stack orderly LbL and repeatedly in the (PAA/GO)(n) films, and about three carbon molecular layers are superposed on each GO sheet. Fourier transform infrared spectra offer evidence for the interaction between the carboxylic groups on PAA and the CTAB on the surface of the GO nanoplatelets. Electrochemistry measurements show that the conductivity of the (PAA/GO)(n) film depends on the carbon-carbon interlayer height of the GO sheet, and the (PAA/GO)(n) film has a typical positive temperature coefficient effect above the PAA melting temperature. The atomic force microscopy images reveal that CTAB molecules stack in a well-ordered head-to-head structure on both surfaces of the GO nanoplatelets and the GO nanoplatelets are embeded between PAA layers.