Shi Jifu

Influence of Preparation Conditions on the Properties of Cu 2 S Photocathodes

Cu2S nanomaterials were prepared, and the influence of preparation conditions on the morphology and catalytic reduction of sodium polysulfide was investigated. The Cu2S photocathode prepared under optimal conditions was used as a quantum-dot-sensitized solar cell. For preparation of the Cu2S photocathodes, HCl pretreatment and reaction with sodium polysulfide were important processes. The Cu2S photocathodes had petal-like structures composed of nano-plates. The Cu2S photocathodes become rough and porous, which increased the surface area, as the HCl concentration increased and pretreatment time was prolonged. As a result, interfacial charge transfer resistance between the Cu2S electrodes and polysulfide electrolyte decreased. Because the reaction between Cu and sodium polysulfide is very fast, the reaction time should be controlled. Otherwise, the Cu2S film will fracture. For good catalytic performance of the Cu2S photocathodes, the best preparation conditions were 30% HCl, pretreatment time for 40 min, and reaction with sodium polysulfide for 10 s. The quantum-dot-sensitized solar cell showed a high photoelectric conversion efficiency of 4.01%.

p -Type and pn -Type Dye-Sensitized Solar Cells

In view of the scientific issues lying behind (1) the p-type dye-sensitized solar cells (DSCs) (the limited dye loading on the NiO film and serious charge recombination between the reduced dyes and the holes generated in the NiO) and (2) pn-type DSCs (mismatching of photoanode and photocathode), we review the recent progress of the electrodes, dyes, and electrolytes for these types of solar cells. The feasible solution of these issues is discussed and, at last, the future development of these types of solar cells is prospected.In view of the scientific issues lying behind (1) the p-type dye-sensitized solar cells (DSCs) (the limited dye loading on the NiO film and serious charge recombination between the reduced dyes and the holes generated in the NiO) and (2) pn-type DSCs (mismatching of photoanode and photocathode), we review the recent progress of the electrodes, dyes, and electrolytes for these types of solar cells. The feasible solution of these issues is discussed and, at last, the future development of these types of solar cells is prospected.

Application of Ionic Liquids with Carboxyl and Aromatic Ring Conjugated Anions in Dye-Sensitized Solar Cells

A method of utilizing p-pi conjugation effects for obtaining low-viscosity ionic liquids is presented. p-pi conjugation effectively disperses anionic charge and reduces Coulombic interactions. Ionic liquids prepared in this study were 1-ethyl-3-methylimidazolium benzoate (EMIB) and 1-ethyl-3-methylimidazolium isonicotinate (EMIIN). They have carboxyl and aromatic ring p-pi conjugated anions, and achieve low viscosities of 42 and 27 mPa . s, respectively. EMIB and EMIIN were employed as electrolytes, which were used to construct dye-sensitized solar cells (DSCs). After optimizing the composition, the ionic conductivity and triiodide ionic diffusion constant for the EMIB-based electrolyte were 1.43 mS . cm(-1) and 1.45 x 10(-7) cm(2) . s(-1), respectively. For the EMIIN-based electrolyte, the ionic conductivity and triiodide ionic diffusion constant were 1.63 mS . cm(-1) and 2.01x10(-7) cm(2) . s(-1), respectively. These were higher than the corresponding values for the EMIB-based electrolyte because of EMIINs lower viscosity. DSCs based on these two electrolytes attained satisfactory energy conversion efficiencies of 2.85% and 4.30% for EMIB and EMIIN, respectively, under an illumination intensity of 300 W . m(-2).

Influence of Preparation Conditions on the Properties of Cu2S Photocathodes

Cu2S nanomaterials were prepared, and the influence of preparation conditions on the morphology and catalytic reduction of sodium polysulfide was investigated. The Cu2S photocathode prepared under optimal conditions was used as a quantum-dot-sensitized solar cell. For preparation of the Cu2S photocathodes, HCl pretreatment and reaction with sodium polysulfide were important processes. The Cu2S photocathodes had petal-like structures composed of nano-plates. The Cu2S photocathodes become rough and porous, which increased the surface area, as the HCl concentration increased and pretreatment time was prolonged. As a result, interfacial charge transfer resistance between the Cu2S electrodes and polysulfide electrolyte decreased. Because the reaction between Cu and sodium polysulfide is very fast, the reaction time should be controlled. Otherwise, the Cu2S film will fracture. For good catalytic performance of the Cu2S photocathodes, the best preparation conditions were 30% HCl, pretreatment time for 40 min, and reaction with sodium polysulfide for 10 s. The quantum-dot-sensitized solar cell showed a high photoelectric conversion efficiency of 4.01%.

Influence of Temperature on the Properties of Polysulfide Electrolyte and Quantum Dot Sensitized Solar Cells

We studied the influence of temperature on the conductivity of a polysulfide electrolyte and the photovoltaic performance of quantum dot sensitized solar cells by electrochemical methods. The results indicate that the conductivity of the electrolyte increases and the diffusion impedance of the polysulfide ions in the electrolyte decreases with an increase in the temperature. Moreover, the photoelectric conversion efficiency of the quantum dot sensitized solar cells decreases when the temperature increases. This phenomenon is mainly caused by a more serious back reaction and the desorption of quantum dots at higher temperatures.