Study On The Design,Preparation Of New Dyes And Their Sensitized Solar Cell Devices

The energy and environment become the key issues of all countries in the world.Solar energy is a clean and continual energy source.Converting solar energy directly into electricity is the most feasible technology.As one member of the third-generation solar cells,dye-sensitized solar cells(DSSCs)have attracted the scientists from many countries with their unique advantages of the low cost and high conversion efficiency.Dye(sensitizer)is the key module of DSSCs,which affects the photovoltaic properties of devices directly by its sensitized ability.Therefore,developing dyes that possess advantages of low costs,environmental friendliness,and excellent sensitized ability becomes the most important in the photovoltaic industry.Compared with traditional PolypyridylRu,the metal-free organic dyes shows many advantages,such as outstanding designability,easier preparation as well as low cost.Among diverse organic dyes,phenothiazine-based dyes stand out by virtue of excellent photoresponse performance,strong electron-donating ability,and a particular butterfly configuration.As another alternative to Polypyridyl Ru,metal-porphyrin photosensitizers put up strong ability of light capture,low cost and excellent photostability.In this thesis,we have designed and prepared three series of phenothiazine-based dyes and two series of metal-porphyrin photosensitizers;then investgated the photovoltaic performance of their solar cell devices in the following areas:Chapter 1: An overview of the renewable energy sources,solar cells,dye-sensitized solar cells and photosensitizers.Chapter 2: Study on the design,preparation and solar cell devices of a new phenothiazine-based D-D-A dye.To enhance the electron-donating ability in the sensitizer molecules,we preparded DP-1 dye possessing the dithiafulvenyl(DTF)unit as the new electron donor.The performances of DP-1 were investigated in comparison with T2-1 by photochemistry,electrochemical,and photovoltaic methods,along with density functional theory(DFT)calculations.From the results,we analyze its structure and point out its deficiency and the improvement direction.Chapter 3: Study on the design,preparation and solar cell devices of newphenothiazine-based D-?-D-A dyes.Based on the conclusion in chapter 2,we have devised and synthesized a series of DPP-dyes with a D-?-D-A structure by introducing ?-spacers of different electrical property and length between DTF and PTZ.The performances of DPP-dyes were systematically investigated by photoelectrochemical and photovoltaic methods,along with density functional theory(DFT)calculations.From the results,we illuminated the important effect of intramolecular torsion angles on improving the electronic transfer in their molecules.Chapter 4: Study on the design,preparation and solar cell devices of new phenothiazine-based D-A-?-A dyes.To improve the intramolecular charge separation,we introduced the D-A-?-A idea to PTZ-based dyes and inserted the benzothiadiazole-phenyl between PTZ and anchor.Additionally,we connected different electron-donors(biphenylamine and alkoxy)and ?-spacer(phenyl)to the other side of PTZ.The systematically investigations about the effects of ?-spacer and different electron-donors were carried out on the photovoltaic methods and density functional theory(DFT)calculation;upon which the mechanism was illuminated.Chapter 5: Study on the design,preparation and solar cell devices of new LYD-series metal-porphyrin dyes.To systematically investigate the effects of different anchors on the photovoltaic properties of metal-porphyrin dyes,we have devised and synthesized a series of LYD-dyes,in which different anchors were connected with Zinc-porphyrin by ethynyl.The performances of their sensitized solar cells have been investigated by optical,photovoltaic,and electrochemical methods.Upon the measurement results and DFT calculations,we demonstrated the rank of diverse anchors and discussed the mechanism and reasons.Chapter 6: Study on the design,preparation and solar cell devices of long-chains metal-porphyrin dyes.Based on the conclusion about the anchor effects in LYD-series dyes,we have devised and synthesized a series of long-chains metal-porphyrin dyes by introducing the best anchor of salicylic acid as well as long alkyl and alkoxy chains.The measurement results showed that the photoelectric conversion efficiency had been improved markedly with better distribution of dyes absorbed onto TiO2 electrode and more effective injection of photoelectrons into TiO2 conduction band.