The New Type Of Arylamine Derivatives As Dye Sensitizers: Experimental And Theoretical Investigation

With coal, oil, natural gas and other non-renewable energy depletion, people began to realize the importance of developing renewable energy. In renewable energy, solar energy gradually has become the focus of attention because of its safety, health, adequate resources and other significant advantages. In 1991,a new type of solar cells—dye-sensitized solar cells(DSSCs) was developed by Swiss federal professor Michael Gr?tzel and his research team, which has attracted extensive attention due to its simple preparation, low costs, and environmental friendly. At present, thephotoelectric conversion efficienciesof DSSCs have reached as high as 13%. In DSSCs, many photoelectrochemical reactions, such as the dye excited by light, electrons injection from the dye to the conductor band of Ti O2, reduction of oxidation state dyes, have occurred in the dye/TiO2 photo-electrode interface, so the study for the interface is of great significance to improve the photoelectric performances ofDSSCs. So, the research on the interface in thisthesis is carried out as follows: Firstly, to explore more promisingsensitizer;Secondly, to study the solvent effects on the dye/TiO2 photo-electrode interface.1. Sensitizer is an important part of DSSCs, which plays an important role in the capturing light and generating the excited electrons. In order to efficiently and quickly find a high-performance sensitizer, density functional theory(DFT) calculations are used to screening three types of arylamine derivatives such as tetrathiafulvalene(TTF), phenothiazines and imidazole based sensitizers. As the calculated results shown,TTFgroup could be used as good electron donor in theorganic sensitizer, which can greatly increase its capability of light-capturing.Byoptimizing the conjugate bridge in phenothiazine based sensitizer, the range of light-absorbing was broadening successfully, which is advantage to improve the photoelectric conversion efficiency.Imidazole based sensitizer for its simple structure and easy preparetion, so the study of subsequent chapters are based this type of sensitizer.2. Theoretical screened imidazole based sensitizers are synthesized successfully, then assembled into the DSSCs were studied. In combination with theoretical calculation and experimental research,the photophysical, electrochemical properties of CDsensitizer, and photovoltaic performances of the corresponding DSSCs are studied, andan atomic level understanding isgivento the different experimental phenomenon between those dyes.The DSSCs based on CD-4 andCD-5has reached the photoelectric conversion efficiencies of 1.89 and 0.61%, respectively. Moreover, when the triphenylamine groups are introduced intoCD-4 andCD-5, the prepared CD-7 andCD-8have obtained thehigher photoelectric conversion efficiencies of 4.11 and 1.51%, respectively. As the research results shown, the introduction of triphenylaminesignificantly enhances the light-capturing capabilities and steric hindrance abilities of CD-4 andCD-5, so as to improvethe photovalticperformances of the corresponding DSSCs.3. Based on imidazole-based sensitizerCD-6, THF and DMF are selected to study the solvent effects on the dye/TiO2 photo-electrode interface and photovalticperformances of DSSCs. When THF and DMF as the solvent are used to prepareCD-6 sensitized TiO2 films, the corresponding DSSCs have obtainedthe photoelectric conversion efficiencies of 1.53 and 0.83%, respectively.As experimental results shown,when THF is used as the solvent, theCD-6 sensitized TiO2 film has a wider range of absorption and greater adsorbed density. Ultimately, the corresponding DSSC has the better photovaltic performance. Besides, the DFT are used to simulatethe effectsof THF and DMF on the adsorbed morphology of CD-6 on TiO2 surface, and an atomic-level explanation is given to the different photovaltic performances of the corresponding DSSCs.