Synthesis Of ZnO、TiO₂Micro/Nanostructure And Their Gas Sensing And Solar Cells Application

Recently, many different size and morphologies of ZnO and TiO₂micro/nano materialsand their applications have been investigated and published. There are many studies oncontrolling the morphology of ZnO since it has many different morphology structures.For the TiO₂,the research was focused on its solar cell application. The synthesis of ZnOand TiO₂micro/nano structure is for the basic study of their properties. Therefore, how tocontrol the synthesis process to fabricate some special morphologies and how to improvethe properties of TiO₂solar cells are the hot topics so far. It will be worthy to modify thesynthesis method of ZnO and TiO₂micro/nano materials, study their crystal structure,morphology and growth mechanism. In this thesis, we will focus on ZnO and TiO₂micro/nano materials, investigate their fabrication method, characterization, growthmechanism, gas sensing property and photovoltaic conversation property, and someworthy results are presented.（1） Synthesis of twinned ZnO microcrystal using hydrothermal method without anytemplate and additive. The growth mechanism of ZnO crystal structure wasinvestigated by changing the reaction temperature and time. Making a gas sensorusing the ZnO production and study its gas sensing properties. The ZnO basedgas sensing device showed excellent sensing properties in20ppm ethanol gas at250C. The sensitivity was6.4, response and recovery time were3s and20s,respectively.（2） The chemical etched Ti mesh screen was embedded into the TiO₂nanoparticlesphotoanode. The properties of DSSCs were studied while their size wasincreasing and compared with the traditional solar cells. We found that the Jsc oftraditional FTO glass based DSSCs decreased from17.90mA/cm2to5.99mA/cm2when the size of cells increased from0.25to9cm2, and the fill factoralso dropped from0.55to0.25. That finally resulted in the conversationefficiency dramatically decreased from7.92%to1.18%. In contrast to that, the Ti mesh screen embedded photoanode presented relatively high efficiency around1.62%at a larger size9cm2.（3） Using the composite structure of TiO₂nanoparticles （TNPs） and anodized TiO₂nanotubes （TNTs） as the photoanode of DSSCs and studying their properties.Comparing the properties of different anode structures, it was found that theTNTs/TNPs anode film on Ti substrate showed higher Jsc⁹.36mA/cm2than theone having⁴.82%efficiency with only TNPs on same substrate. The traditionalFTO based DSSC presented higher Jsc and efficiency when its size was smallerthan1cm2. When the size was increased to9cm2, the conversation efficiency wassignificantly dropped from7.92to1.18%. However, the Ti based TNTs/TNPsanode showed a little lower Jsc and efficiency when its size was small, but itgave a much higher efficiency at a larger size with².92%efficiency than theFTO based cell. It indicates that the Ti based TNTs/TNPs anode could keep itsefficiency at a relatively high value when the size of the cells increased.（4） Making a TiO₂nanoparticles paste with0.2wt%carbon nanotubes （CNTs） addedand investigating its photovoltaic properties. Four different kinds of photoanodeswere fabricated, they were （CNTs+TNPs） paste/TNTs/Ti,（CNTs+TNPs） paste/Ti,TNPs paste/TNTs/Ti and TNPs paste/Ti. After comparing the properties of thosefour kinds of cells, we found that the （CNTs+TNPs） paste/TNTs/Ti had thehighest Jsc¹4.27mA/cm²and efficiency⁶.34%.It was obvious that the CNT-added TiO₂paste composite with anodized TNTs photoanode could improve theenergy conversation efficiency of DSSCs.