Investigation On New Phenothiazine Organic Dyes For DSSC Devices

Owning to environmentally friendly and inexpensive production,dye-sensitized solar cell(DSSC)has become a hot topic for scientists.Dye sensitizer is one of the key compenent in DSSC device,which harvests sunlight and partially determines DSSC performance.Currently,dyes of heavy metal complexes(e.g.ruthenium based dyes)are the mainstream photo sensitizers in DSSC devices due to their high device efficiency.However,the limited availability of ruthenium and the low stability of ruthenium based dyes could hinder the commercialization of DSSCs.The metal-free organic dyes have many advantages e.g.easy molecular-structure tuning,widely available,easy to purify,etc.However,currently the efficiency of pure organic dye-sensitized solar cells still has room to improve and further study is demanding.This thesis focuses on the investigation of four new metal-free organic photosensitizer for DSSC devices,and the relationship between molecular stucture and material properties is explored.There are mainly three parts in this work:(1)Design,synthesis and characterization of dyes.In this part,the four target products,i.e.3-(9H-Carbazol-9-y1)Phenyl-7-(N-ethyl-10H-phenothiazine-3-cyanoacrylic acid)(CBPTZ1),3-(9H-Carbazol-9-y1)Phenyl-7-(N-hexyl-10H-phenothiazine-3-cyanoacrylic acid)(CBPTZ2),3-(9H-Carbazol-9-y1)Phenyl-7-(N-hexyl-10H-phenothiazine-rhodanine-3-aceticacid(CBPTR1)and 4-(9H-Carbazol-9-y1)Phenyl-7-(N-hexyl-10H-phenothiazine-rhodanine-3-acetic acid(CBPTR2)were prepared by chemical bonding of different potential functional groups and using various types of reactions.Then these four materials were structurely characterized,including nuclear magnetic resonance,mass spectrometry,and infrared spectroscopy.(2)Investigation on DSSC devices based on CBPTZ1 and CBPTZ2.CBPTZ1 and CBPTZ2 are two new D-?-A type metal-free organic dyes with phenothiazine as ?-bridge,carbazole as electron donor and 2-cyanoacrylic acid as electron-acceptor and anchor group.They were used as sensitizers for DSSCs with TiO2 anode prepared by electrospray method.By adjusting the experimental temperature,the best efficiency of device based on CBPTZ2 was obtained(9.84%).In this part,dye loading and device performance as well as the alternative-current impedance of these two dyes and the incident photon-to-electron conversion efficiency were investigated.(3)Investigation on DSSC devices based on CBPTR1 and CBPTR2.CBPTR1 and CBPTR2 are anothor two new D-?-A type metal-free organic dyes.The difference betwwen the above studied dyes of CBPTZ1/CBPTZ2 and dyes of this section lies in the different electron-acceptor/anchor group,e.g.,the former is 2-cyanoacrylic acid;while the latter is rhodanine-3-acetic acid.The study of this part includes the optophysical property,single dye based DSSC device and the alternative-current impedance for devices.It turned out that the performance of DSSC based on CBPTR1 and CBPTR2 is not as good as the previous dyes,with efficiencies of 3.1% for CBPTR1 and 3.8% for CBPTR2.Possible reasons were analyzed.