Study On Porphyrin Sensitizer And Cobalt-based Electrolyte In Dye-sensitized Solar Cells

Dye-sensitized solar cells(DSSC) can be easily manufactured from low-cost,earth-abundant, and environmentally friendly materials makes them particularly attractive.They are promising alternatives to silicon-based and thin-film photovoltaic technologies for solar energy conversion.Porphyrin dyes have became a hotspot in the field of Dye-sensitized solar cells(DSSCs) due to their better light responsiveness, higher molar absorption coefficient,better chemical stability, etc, during the past few years. However, the iodine electrolyte redox couple system has its own disadvantages, which limit further efficiency improvement of DSSC. The use of cobalt complexes-based electrolytes has very recently brought forth a new opportunity towards efficiency enhancement of DSSC.This work is a part of the National Basic Research Program of China(Grant NO.2011CBA00701) and National Nature Science Foundation of China(Grant NO.21171084).Some valuing and significant results were obtained in the following subjects.1. Theoretical study on the ZnYD series molecules The molecular orbital energy levels of electron donor Zn YDR and electron acceptors B-H were studied using B3LYP/LANL2 DZ method at the density functional theory(DFT).And then the sensitier candidates were calculated using density functional theory(DFT) and time-dependent DFT(TD-DFT) calculations. The molecular orbital energy levels, the molecular orbital spatial distributions and the electronic absorption spectra of the Zn YD series molecules were compared with those of YD2-o-C8 and SM315 to reveal the substituent effects of different acceptor groups on the porphyrin compounds and select good sesitizer candidates. The results show that all of these compounds have considerably smaller orbital energy gaps, better charge-separated states and red-shifted absorption bands,causing them to absorb photons in the lower energy region. The Zn YD series sensitizer candidates screened in the current work are very promising for providing good performance and might even challenge the photoelectric conversion efficiency record of12.3% for porphyrin sensitizers. In addition, a new absorption band emerges in the600~700 nm region, which makes it possible for them to become panchromatic,and we speculated the result of absorption band emerging in the 600~700 nm region is piazthiole because one thing all porphyrin sensitizer candidates have in common is they contain piazthiole in their structures including SM315.2. Theoretical study on the Zn SM series molecules In this chapter, we designed a series of Zn SM porphyrin sensitizer candidates with same donor and different acceptors, and they were calculated using density functional theory(DFT) and time-dependent DFT(TD-DFT) calculations. The molecular orbital energy levels, the molecular orbital spatial distributions and the electronic absorption spectra of the Zn SM series molecules were compared with those of YD2-o-C8 and SM315 to reveal the substituent effects of different acceptor groups on the porphyrin compounds and select good sesitizer candidates. The results show that all of these compounds have considerably smaller orbital energy gaps, better charge-separated states and red-shifted absorption bands, causing them to absorb photons in the lower energy region. The Zn SM series sensitizer candidates screened in the current work are very promising for providing good performance and might even challenge the photoelectric conversion efficiency record of 12.3% or 13% for porphyrin sensitizers. In addition,a new absorption band emerges in the 650~680 nm region, which makes it possible for them to become panchromatic,and we speculated the result of absorption band emerging in the 650~680 nm region is piazthiole because one thing all porphyrin sensitizer candidates have in common is they contain piazthiole in their structures including SM315.3. Theoretical study on the Zn Por series molecules We designed a series of Zn Por porphyrin sensitizer candidates with same donor and different acceptors in this chapter, and they were calculated using density functional theory(DFT) and time-dependent DFT(TD-DFT) calculations. The molecular orbital energy levels, the molecular orbital spatial distributions and the electronic absorption spectra of the Zn Por series molecules were compared with those of YD2-o-C8 and SM315 to reveal the substituent effects of different acceptor groups on the porphyrin compounds and select good sesitizer candidates. The results show that all of these compounds have considerably smaller orbital energy gaps, better charge-separated states and red-shifted absorption bands,causing them to absorb photons in the lower energy region. The Zn Por series sensitizer candidates screened in the current work are very promising for providing good performance and might even challenge the photoelectric conversion efficiency record of12.3% or 13% for porphyrin sensitizers. In addition,a new absorption band emerges in the650~670 nm region, which makes it possible for them to become panchromatic,and we speculated the result of absorption band emerging in the 650~670 nm region is piazthiole because one thing all porphyrin sensitizer candidates have in common is they contain piazthiole in their structures including SM315.4. Theoretical study on the Co Tpy series molecules A series of Co Tpy porphyrin sensitizer candidates with same donor and different acceptors were designed in this chapter, and they were calculated using density functional theory(DFT) and time-dependent DFT(TD-DFT) calculations. The molecular orbital energy and the electronic absorption spectra were compared with FK269 to reveal the substituent effects of different groups on the compounds and select good candidates. The results show that eight of these compounds have higher occupied molecular orbital(HOMO)than FK269 and two compounds have smaller electronic absorption.5. Synthesis of 1,3-bis(pyridin-2-yl) pyrazole A new method of synthesis of 1,3-bis(pyridin-2-yl) pyrazole is provided. it has changed the past the complex synthesis method and overcomed the deficiency of the traditional process. Lower cost, simple operation, saving time are advantages of the method, it not only made the product purified easily, but also greatly improved the yield of the synthesis. It provided a possible to use simple method to synthesis more ligand including pyrazole and league pyridine class.