Synthesis And Photoelectrochemical Properties Investigation Of Nano-micro Structure Ln₂S₃, TiO₂/In₂S₃Films

Among the effective use of solar energy, photovoltaic solar cells is the fastestgrowing and the most vibrant research area in recent years. Although there are varioustypes of solar cells, complex manufacture process and environmental pollution are themain problems yet. Hence, improving the photoelectric conversion efficiency,reducing the production cost and solving the problem of the environmental pollutionare still critical issues for human beings.β-In₂S₃is a nontoxic semiconductor with band gap of2.0².3eV, which hasgreat potential for photovoltaic applications owing to its excellent optical, electricaland photoelectrochamical properties. Recently, it was reported that the CIGS solarcells prepared using β-In₂S₃as buffer layer instead of CdS showed16.4%conversionefficiency, which was close to the typical solar cell using a CdS buffer layer (19.9%).Presently, In₂S₃thin films are prepared by chemical bath method, which generallyresult in the poor crystallinity and adhesion with the substrate. Further, theextra-annealing process would complex the preparation and increases the cost. On theother hand, there are seldom reports on the photoelectrochemical properties of In₂S₃thin films. Herein, the preparation and the photoelectrochemical properties of In₂S₃thin films were investigated. The main content and innovation of this thesis are list asfollowing:1. For the first time, the In₂S₃thin films composed of nano-/microflakes werefabricated on FTO substrate when L-cystine was used as the S source in the hydrothermal system. By investigaing the samples obtained with different experimentparameters, we found that the morphology of the films can be controlled by adjust thereaction time, the reactant contration ratio and the reation temperature. A possiblegrowth process of the films was also proposed.2. The photoeletrochemical properties of the time-dependent films wereinvestigated. It was found that the films prepared for12h achieved a photocurrentdensity of about0.07mA·cm2. However, the highest photoelectric conversionefficiency0.01%was obtained for the6h-synthesized film.3. When the In₂S₃films prepared at160℃for12h were annealed at500℃for3h, In₂O₃films with similar morphology to the In₂S₃films were obtained. Thisdemonstrated that it is an effective way to obtain the morphology-controlled In₂O₃thin films by oxiding the In₂S₃thin films.4. The In₂S₃thin films composed of wedgelike crystals were fabricated on FTOsubstrate when thiourea was used as the S source with the assistant of tartaric acid inthe hydrothermal system. The crucial role of tartaric acid on the film formation wasstudied detailedly. A possible formation mechanism of the films was also proposed byanalyzing the time-dependent thin films. The photoelectrochemical measurementresults showed a photocurrent up to0.48mA·cm^-2, which is higher than that of theflakelike In₂S₃thin films.5. The TiO₂/In₂S₃core/shell nanorod arrays photoelectrodes were prepared bytwo step method. The TiO₂nanorod array films were synthesized by a hydrothermalmethod. And In₂S₃thin films were deposited on TiO₂nanorods by SILAR method.Finally, the resulting films were annealed in N2atmosphere in order to get a bettercrystallinity. The optical and photoelectrochemical measurement results demonstratedthat the absorbance range was extensively extended in the visible light region for theIn₂S₃-sensitized TiO₂thin films, and the photo activity was enhanced significantly. Aphoto current of1.07mA·cm^-2and a photoelectric conversion efficiency of0.33%were obtained. Furthermore, the photoelectric conversion efficiency mechanism wasalso discussed.