Preparation And Application Of Photoelectric Conversion Functional TiO₂ Materials

Titanium dioxide(TiO₂) has attracted great attentions as a photoelectricsemiconductor material due to its excellent photoelectric conversion ability andphysicochemical property. It has been widely investigated and employed in manyfelds such as optoelectronic device, wastewater treatment, air purification andantifogging antibacterial material.When exposed to the light which has morepower than its band gap, TiO₂ produces electrons and hole pairs, thephotoelectrons transfer to the surface of the material and then the separation of thephoto-generated carriers and the photoelectric conversion of TiO₂ electrode arerealized. Most of the organic compounds and some metal ions can be oxidized andreduced effectively because of the strong oxidative ability of the photoholesproduced by the transference of photoelectrons and the reductive ability of theconduction band electrons, which has a vital meaning in the field of environmentprotection. Consequently, the investigation and preparation of functional TiO₂materials with proper characteristics are very meaningful works.In this thesis, sensitized nanocrystalline TiO₂ porous film photoelectrodeswith excellent properties were prepared via sol-gel method and screen printingtechnique. Its surface microscopic characteristics and photoelectricity werecharacterized by field emission scanning electron microscope, x-ray diffraction,high resolution electron microscopy, solar energy battery spectrum, etc.Meanwhile, TiO₂ photocatalysis material was synthesized via sol-gel method andultraviolet photo-assisted method, which was also characterized by x-raydiffraction, laser raman spectrum, x-ray photoelectron spectroscopy, highresolution electron microscopy, field emission scanning electron microscope,etc.And many significant results were gained by comparing the structure and theperformance with traditional ones synthesized via sol-gel method.The two aspects mentioned above provided affirmative mind and direction to use sunlighteffectively, and offered a new method to solve questions of visible-lightphotocatalysis properly.Dye-sensitized nanocrystalline TiO₂ porous film photoelectrodes wereprepared via sol-gel method. The investigation of the preparing process showedthat the photoelectric properties of the solar cells composed of film electrodeprepared via coating method were outstanding on the condition that the colloidcontent was 15% and the thickness of the film electrode was 7～9μm, and thephotoelectric conversion efficiency could reach 4.6%.nanocrystalline TiO₂ porousfilm photoelectrodes were prepared via sol-gel method and screen printingtechnique. The property of the film electrode prepared using ethyl cellulose asthickener was better and the photoelectric conversion efficiencythe of the solarcells prepared by which is about 5.05%. The results also showed that thephotoelectric conversion efficiency of the TiO₂ porous film electrode made ofethyl cellulosic thichener, rheological angent (AS, BT and C3) could be 5.27%respectively.the optimum technological parameters were decided through a largequantity of experimental studies such as the optimization of solid content of TiO₂,eyelet number, screen printing times, hydrothermal time, reaction environment,sintering procedure, and the choice of electrolytes. The photoelectric conversionefficiency with the optimized film electrode could be 6.25%. And thephotoelectric conversion efficiency could be increased from 5.27% to 6.72%when the surface of the dye-sensitized nanocrystalline TiO₂ porous filmphotoelectrodes were modified.The introducing of the ultraviolet radiation into the sol-gel process promotedthe transformation of TiO₂ from amorphous structure to anatase phase, anataseTiO₂ catalyst could be prepared at 100℃and the crystallization degree of theanatase particle was increased significantly with less particle size distribution and larger specific surface area.TiO₂compound catalyst synthesized using aphoto-assisted technique had obvious spectral response in the visible region andcould catalyzed degrade many kinds of organic pollutant molecules.Photo-catalytic activity was studied by observing the ultraviolet photocatalysisdegradation of rhodamine B, and the result showed that the catalytic activity ofthe photo-assisted samples were obviously higher than that of normal ones.The results and conclusions above showed that the integration of the relatedtechnology and the traditional sol-gel method from different angles in the field oftunable synthesis of TiO₂ semiconducting material with high activity providedmeaningful theoretical research and exploration for developing and utilizing thephotoelectric material and the photocatalysis material effectively.