En Mei Jin

Photosensitization of nanoporous TiO2 films with natural dye

Dye-sensitized solar cells were assembled by using natural dyes extracted from wormwood, bamboo leaves and red maple leaves as photosensitizers. The Voc values of natural dyes from wormwood, bamboo leaves and maple leaves were 0.67, 0.66 and 0.59, respectively. The ISC values were varied from 2.56 to 5.95 mA cm−2 and the fill factors from 56 to 66%. Based on investigations into the structure and properties of dye molecules, wormwood revealed the best photosensitized effects among several kinds of natural dyes, which is due to the interaction between the carbonyl and hydroxyl groups of anthocyanin and the surface of TiO2; these wormwood extracts act as efficient sensitizers.

Enhancement of the photoelectric performance of dye-sensitized solar cells using Ag-doped TiO2 nanofibers in a TiO2 film as electrode.

For high solar conversion efficiency of dye-sensitized solar cells [DSSCs], TiO2 nanofiber [TN] and Ag-doped TiO2 nanofiber [ATN] have been extended to be included in TiO2 films to increase the amount of dye loading for a higher short-circuit current. The ATN was used on affected DSSCs to increase the open circuit voltage. This process had enhanced the exit in dye molecules which were rapidly split into electrons, and the DSSCs with ATN stop the recombination of the electronic process. The conversion efficiency of TiO2 photoelectrode-based DSSCs was 4.74%; it was increased to 6.13% after adding 5 wt.% ATN into TiO2 films. The electron lifetime of DSSCs with ATN increased from 0.29 to 0.34 s and that electron recombination was reduced.

Increases in solar conversion efficiencies of the ZrO2 nanofiber-doped TiO2 photoelectrode for dye-sensitized solar cells

In this paper, in order to improve the efficiency of dye-sensitized solar cells, we introduced zirconia [ZrO2] nanofibers into a mesoporous titania [TiO2] photoelectrode. The photoelectrode consists of a few weight percent of ZrO2 nanofibers and a mesoporous TiO2 powder. The mixed ZrO2 nanofibers and the mesoporous TiO2 powder possessed a larger surface area than the corresponding mesoporous TiO2 powder. The optimum ratio of the ZrO2 nanofiber was 5 wt.%. The 5 wt.% ZrO2-mixed device could get a short-circuit photocurrent density of 15.9 mA/cm2, an open-circuit photovoltage of 0.69 V, a fill factor of 0.60, and a light-to-electricity conversion efficiency of 6.5% under irradiation of AM 1.5 (100 mW/cm2).

PHOTOVOLTAIC PROPERTIES OF TiO2 PHOTOELECTRODE PREPARED BY USING LIQUID PEG-EEM BINDER

We present one of the central and basic factors related to the TiO2 photoanodes of optimal absorption site. Binder is of particular importance for surfaces and interfaces that involve organic dye and TiO2 layer. We introduced monodispersed liquid copolymer binders; poly(ethylene glycol)-ethyl ether methacrylate (PEG-EEM) instead of solid PEG to increase TiO2 electrodes surface area. We attempt to investigate the morphology of the photoanodes and photovoltaic effects using field emission scanning electron microscopy (FE-SEM), BET and photovoltaic properties under illumination with AM 1.5 simulated sunlight. We achieve 167% enhanced power conversion efficiency when the optimal content of liquid PEG-EEM binder was 4 wt.% than that of PEG binder. We show that the performance of Dye-sensitized solar cell (DSSC) can be strongly improved using liquid type binder.

Preparation and Electrochemical Properties of LiFePO 4 - PSS Composite Cathode for Lithium-ion Batteries

In this study, we prepared - poly (sodium 4-styrenesulfonate) (PSS) composite by the hydrothermal method and ball-milling process. Different wt% PSS were added to . The cathode electrodes were made from mixtures of -PSS: SP-270: PVDF in a weighting ratio of 70%: 25%: 5%. -PSS powders were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). The electrochemical properties of -PSS/Li batteries were analyzed by cyclic voltammetry, charge/discharge tests, and AC impedance spectroscopy. A Li/-PSS battery with 4.75 wt% PSS shows the best electrochemical properties, with a discharge capacity of 128 mAh/g.

COATING THE CONDUCTIVITY MATERIALS TO IMPROVING THE ELECTROCHEMICAL PROPERTIES OF LiFePO4

LiFePO4 cathode materials were prepared by a solid-state method followed by one-step heat treatment. To improve the electrochemical properties of the LiFePO4, acetylene black (AB), citric acid (CA), and pyrene are added as carbon source, respectively. The cyclic voltammetry (CV), AC impedance and galvanostatic charge/discharge testing results showed that using the LiFePO4-C composite such as the AB carbon source exhibits higher discharge capacity and stability than the other composite. Synthesized LiFePO4-C/Li cells (with AB) showed that initial discharge capacity was 140.65 mA h g-1 and at the 2nd cycle were 145.87 mA h g-1, respectively. Morphology and electrochemical performance of the LiFePO4 cathode materials were investigated. Furthermore, the cell was subjected to current density studies (0.1 mA cm-2) that suggested excellent capacity retention of the cell at 25°C.

Preparation and Characterization of Chitosan Binder-Based Electrode for Dye-Sensitized Solar Cells

A chitosan binder-based TiO2 photoelectrode is used in dye-sensitized solar cells (DSSCs). Field-emission scanning electron microscope (FE-SEM) images revealed that the grain size, thickness, and distribution of TiO2 films are affected by the chitosan content. With addition of 2.0 wt% chitosan to the TiO2 film (D2), the surface pore size became the smallest, and the pores were fairly evenly distributed. The electron transit time, electron recombination lifetime, diffusion coefficient, and diffusion length were analyzed by IMVS and IMPS. The best DSSC, with 2.0 wt% chitosan addition to the TiO2 film, had a shorter electron transit time, longer electron recombination lifetime, and larger diffusion coefficient and diffusion length than the other samples. The results of 2.0 wt% chitosan-added TiO2 DSSCs are an electron transit time of  s, electron recombination lifetime of  s, diffusion coefficient of  cm2 s−1, diffusion length of 14.81 μm, and a solar conversion efficiency of 4.18%.

Study of the Characteristics of Low-Temperature Prepared TiO 2 Paste for Dye-sensitized Solar Cells

In this paper, we have developed a low temperature process to make two type of paste by using nanoparticles(P25). The interconnections between substrate and films or link between particles of free-binder paste(FP1, FP2, FP3) is very poor. Therefore, the Titanium(IV) isopropoxide was added to the TP paste to improve the interconnection. Electron transport time () and recombination time () are analyzed by IMPS (intensity-modulated photocurrent spectroscopy) and IMVS(Intensity-modulated photovoltage spectroscopy). In the results, of TP paste based DSSCs (about ) is faster than other samples. is longer from s of FP2 to s of TP. A solar conversion efficiency (DSSCs) of TP is 3.54% for an incident solar energy of 100 mW (meanwhile, 2.70% for DSSCs with FP2). The conversion efficiency is increased by 1.3 times.

Optimized for Low-temperature Sintering of TiO 2 Paste with TTIP

In this paper, the low-temperature sintering of is approached to solve the problem of high temperature sintering which decreases the interconnection between particles or between substrate and particle. paste is prepared with Titanium (IV) isopropoxide as the precursor material and calcinate at different conditions (low temperature). In the results, since the changing of temperature and time of sintering, crystalline phase do not change and the intensities of anatase, rutile phase are higher. At , 7 h sintering condition, crystalline size of anatase and rutile phase are the smallest which are 13.07 and 17.47 nm, respectively. In addition, the highest zeta potential is about 32.77 mV and the repulsive force increases thus leading to the best of the dispersion characteristics between particles. Futhermore, DSSCs at that condition exhibits the highest efficiency with the values of , , FF and are 0.69 V, , 67.93% and 4.06%, respectively.

Electrochemical Properties of Dye-sensitized Solar Cells with Improving the Surface Structure

We use UV(ultraviolet)- treatment to increase the surface area and porosity of films in dye-sensitized solar cells (DSSCs). After the UV- treatment, surface area and porosity of the films were increased, the increased porosity lead to amount of dye loading and solar conversion efficiency was improved. Field emission scanning electron microscopy images clearly showed that the nanocrystalline porosity of films were increased by UV- treatment. The Brunauer, Emmett, and Teller surface area of the films were increased from to by using UV- treatment for 20 min. Also, UV- treatment of films significantly enhanced their solar conversion efficiency. The efficiency of the films without treatment was 4.9%, and was increased to 5.6% by UV- treatment for 20 min. Therefore the process enhanced the solar conversion efficiency of DSSCs, and can be used to develop high sensitivity DSSCs.