Beibei Ma

Mg(OOCCH3)2 Interface Modification after Sensitization to Improve Performance in Quasi-solid Dye-Sensitized Solar Cells

In this paper, a simple yet efficient method is proposed to improve the performance of dye-sensitized solar cells (DSCs) by modification after sensitization using Mg(OOCCH(3))(2). With modification of Mg(OOCCH(3))(2), a blue shift of the absorption peak and optical band gap were observed in the UV-vis spectrum. As shown in the Fourier transform infrared spectrum, the intermolecular hydrogen bonding of N3 dye, which caused the aggregation of dye molecules, was weakened. As shown in the I-V characteristic, the conversion efficiency of the DSCs was improved by the treatment of Mg(OOCCH(3))(2). Furthermore, the charge recombination was retarded as evidenced by the decreased dark current and the slowed decay rate of the dye excited state, which were characterized by the I-V curve in dark and transient photovoltage spectra. The mechanism of this modification process was also proposed further. Modification with Mg(OOCCH(3))(2) facilitated the electron injection from the dye molecule to the conductive band of TiO(2) by raising the excited state energy level of the dye molecule. This energy level rising was evidenced by the results of the cyclic voltammetry test and the blue shift of the optical band gap. Furthermore, Mg(OOCCH(3))(2) worked as an insulating barrier layer at the sensitized TiO(2)/electrolyte interface, thereby retarding the charge recombination in DSCs.

Constructing nanorod–nanoparticles hierarchical structure at low temperature as photoanodes for dye-sensitized solar cells: combining relatively fast electron transport and high dye-loading together

ZnO nanorod–nanoparticles (NR–NPs) hierarchical structure was prepared via a two-step hydrothermal process at 70 °C. In the hierarchical structure, ZnO nanorods prepared at step one served as the backbone for direct electron transport while ZnO nanoparticles synthesized at step two offered large surface area for dye-loading. Both reaction temperature and reaction time at step two had a significant influence on the morphology of the product. At a higher temperature, microspheres appeared above the nanorod film instead of nanoparticles surrounding the nanorods. Prolonging the reaction time to 24 h, the NR–NPs structure would transform to nanorod–nanoplants. Intensity-modulated photocurrent spectroscopy results showed that the photoanode composed of the NR–NPs hierarchical structure had an electron diffusion coefficient (Dn) much higher than that of the nanoparticles. The dye desorption results showed that the dye adsorption amount for the NR–NPs structure was as much as 250% of that for the nanorods. Compared with dye-sensitized solar cells (DSCs) based on nanorods, the incident photon-to-electron conversion efficiency of the DSCs based on NR–NPs hierarchical structure improved remarkably. Under AM 1.5G illumination (100 mW cm−2), the power conversion efficiency of DSCs based on photoanodes composed of NR–NPs hierarchical structure exhibited a significant improvement (more than 120%) compared with that of ZnO nanorods.

Inorganic iodide ligands in ex situ PbS quantum dot sensitized solar cells with I−/I3− electrolytes

In this paper, inorganic iodide ligands were used in PbS quantum dot sensitized solar cells (QDSCs) with iodide/triiodide electrolytes. Inorganic ligands are employed to replace organic ligands in QDSCs for the first time. They combined effects of passivating surface states and decreasing the interface resistance between QDs and sensitized TiO2, QDs and electrolyte. Then the corrosion of PbS QDs by triiodide in iodide/triiodide electrolytes was suppressed and electron injection and hole transfer was much easier. Stability test verified iodide ligands could prevent PbS from corrosion of iodide/triiodide electrolytes. Electrochemical impedance spectroscopy (EIS) showed that iodide ligands effectively decreased the interface resistance and improved the electron transfer. Finally, the performance with iodide ligands was significantly improved and achieved 3.7 times that of the untreated cells in efficiency.

A simple and efficient method using polymer dispersion to prepare controllable nanoporous TiO2 anodes for dye-sensitized solar cells.

An efficient method using a polymer dispersion (PD) based on a copolymer of styrene and butyl acrylate to prepare TiO2 electrodes for dye-sensitized solar cells (DSCs) was introduced. The obtained TiO2 nanoporous film was investigated by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. A porous structure with pore size distribution from tens of nanometers to several hundred nanometers or even micrometers was characterized. This offered the film a feature of high haze factor and porosity. When using the film as photoanode, a quasi-solid-state DSC was successfully fabricated. The device showed an improved per-weight-efficiency by a factor of 2.7, resulting from the reduced interfacial resistance and the enhanced light scattering effect revealed by electrochemical impedance spectroscopy and transmittance spectroscopy, respectively. The developed PD-based colloid is promising to be applied in production on a large scale as a result of its simple prescription and stability during storage. A proposal to further improve the porous film is also introduced at the end of the paper.

Structure and Morphology of Nanosized PbS on TiO2 Nanoporous Film in Dye-Sensitized Solar Cells

The structure and morphology of nanosized PbS were studied, by high-resolution transmission electron microscope (HR-TEM) and X-ray diffraction (XRD) analysis. A three-layer coating of nanosized PbS was synthesized by an in situ method on TiO2 films. The results showed that in the PbS clusters, 2–3 nm particles form the major part, although some 3–10 nm particles also existed. The sizes of the particles distributed in a certain range. Such distribution played an important role in the surface modification of dye-sensitized solar cells.

Alumina Post-Modification After Dye-Sensitization: Effect on the Performance of Quasi-Solid State Solar Cells

In this paper, dye-sensitized TiO2 electrodes were immersed into a solution of aluminum isopropoxide and after hydrolysis quasi-solid state solar cells were fabricated. The interaction between the dye and the resulting Al2O3 overlayer was investigated by ultraviolet-visible (UV-vis) spectrum and X-ray photoelectron spectrum (XPS). I-V characteristics showed that the overlayer greatly increased photovoltage and slightly decreased photocurrent under irradiation of low intensity, and increased both photovoltage and photocurrent under AM 1.5 irradiation. The Al2O3 overlayer at the dye/electrolyte interface results in a 28% improvement in overall photo-to-electrical conversion efficiency from 2.60% to 3.32% under illumination of light intensity 100 mW/cm2. Dark current measurements show that Al2O3 acting as insulator barriers to retard recombination between TiO2, dye/quasi-solid state electrolyte interface.

Structure and Morphology of Quantum Dots Modifying Tio2 Nanoporous Film in Dye-Sensitized Solar Cells

In this paper, A three-layer coating nano-sized PbS was synthesized by an in-situ method on TiO2 films. The structure and morphology of nano-sized PbS was studied, characterizations such as TEM and XRD were used. The results indicated that in the PbS clusters, particles of 2-3 nm take the principle part, while some 3-10 nm particles also exist. Such distribution played an important role in interface modifying dye-sensitized solar cells, and the nano-sized PbS modification results in a 21% improvement in overall photo-to-electrical conversion efficiency of the dye-sensitized solar cells