Co-sensitization Of Dye Sensitized Solar Cells With Imine And N719 And Their Photoelectrical Properties

Dye sensitized solar cell(DSSCs) as an effective solar energy utilization route has become the main direction of the new generation solar cell research. While traditional ruthenium dye N719 sensitized solar cells exist the problems such as weak absorption in the blue violet region and competition absorption of the electrolyte around 380 nm, which affecting the further improvement of the cell efficiency. Therefore, choosing and synthesis of a series of imine compounds which are compatible to N719 as co-sensitizers to achieve spectral compensation, enhancing spectral response and compensation competitive absorption is an effective way to improve the performance of ruthenium dye sensitized solar cells.In this thesis, three bis(o-pyridinemethylene) benzenediamine have firstly been screened and synthesized as sensitizers, and their optical and electrochemical properties, spectral compensation, competitive absorption compensation and energy matching were studied to examine whether they are suitable for N719 sensitized DSSCs system, then the reasons for the change of the performance were studied from the aspects of electron recombination and electron lifetime. The reasons for the difference of the three kinds of co-sensitizer were analyzed from the perspective of molecular structure and the effect of different metal complexes on the co-sensitization performance is studied by means of the transition metal complexes. The results showed that adjacent pyridine diimine benzene can improve the utilization of N719 on blue violet region 300-450 nm, compensate for competitive absorption of I3– around 380 nm, reduce the electron recombination, and prolong the lifetime of electron, which resulted high photoelectric properties. This kind of co-sensitizer can improve the performance of N719 sensitiaed solar cells by 30%. After coordination with transition metal, the performance is lower but still higher than N719 sensitized solar cells.Three different amines source of 1,2-diaminobenzene, 1,2-diaminocyclohexane and 1,4-butanediamine were used to prepare rigid, semi-rigid and flexible bis(o-pyridinemethylene)benzenediamine co-sensitizers, respectively. The adaptability in N719 sensitized solar cells, the effects of molecular rigidity and coordination with different metal on the performance of DSSCs were studied. The results show that these three kinds of co-sensitizer are suitable to use in N719 sensitized solar cellsl. The co-sensitization performance of the rigid co-sensitizer with large conjugate system is better than that of semi-rigid and flexible co-sensitizers. The performance of N719 sensitized solar cell could be improved by 30% with rigid co-sensitizer. After coordination with transition metal, the performance is much different.A series of 2,6-bis(iminoakyl)pyridine with stronger rigidity and larger conjugate system were selected and synthesized, and they were examined to determine whether they are suitable for the N719 sensitized solar cell system from the aspects of spectral compensation, spectral response enhancement, competitive absorption compensation and energy level matching. The reasons for the improvement of the performance of DSSCs were studied from the aspects of dye aggregation, electron recombination, electron lifetime and electron transport, and the effects of different alkyl substituents, different positions and number of the same alkyl group, and metal coordination on the performance of the co-sensitized cells were also studied. The result shows that 2,6-bis(iminoakyl)pyridine can alleviate the aggregation of N719, enhance the spectral response and inhibit the recombination of injected electrons with electrolyte, so as to improve the performance of DSSCs. Different positions and the number of the alkyl groups are two main factors that affect the co-sensitization. After coordination with metal, the performance of DSSCs was not found improve too much. The performance of N719 sensitized solar cell could be improved by 35% with 2,6-bis(iminoakyl)pyridine co-sensitizer.Another co-sensitizer rubrene with much larger conjugate system was screened and applied to N719 sensitized solar cells. It is found that rubrene can compensate the absorption of N719 in the region of 300-750 nm and increase the utilization of light, its excellent electron transport properties and matching level distribution could greatly improve the short circuit current density, and it could also effectively inhibit electron recombination, prolong the electron life, and thus improve the open circuit voltage value. The performance of N719 sensitized solar cell could be improved by 40% with rubrene.The performance of N719 sensitized solar cell can be greatly improved by employing the organic compounds of imine as co-sensitizer. The molecular structure of the co-sensitizer has important influence on the co-sensitization performance, and it is very important to choose the suitable molecular structure in the selection process of the co-sensitizer. Generally, the co-sensitizer with high rigidity, good coplanarity and large conjugated system will obtain better performance.