Design And Syntheses Of Triphenylamine-Based Dye Sensitizers

The development of solar energy provides a new way to solve the world’s energy problems. Reducing the cost of pv cells is a good way to exploit solar energy more efficiently. Dye-sensitized solar cells(DSSCs) can achieve this requirement, but the efficiency of current DSSCs have still need to be further improved.In order to improve the photoelectric conversion rate of dye sensitizer, this dissertation designed and synthesized two series triphenylamine-based organic compounds. Their optical, electrical, physical and chemical properties were studied in detail.Chapter 1 introduced the research progress of co-sensitized solar cell including Ru complexes, Phthalocyanine, Porphyrin dyes. The mechanisms of photocurrent generation and the impact factors on battery efficiency were also introduced in detail. In addition, the previous design idea of dye sensitizer was summarized in brief.Chapter 2 introduced the design strategy of dye sensitizer of this dissertation in detail. The required HOMO, LUMO energy level and energy band range of compounds we plan to synthesize were put forward based on the energy level distribution of cell module. On this basis, several series of molecular structure were designed. Their quantum calculations were performed using density functional theory(DFT) with the B3 LYP in conjunction with the 6-31G(d) basis set on the Gaussian 09 program package. The calculated HOMO and LUMO energy level of all molecules were analyzed in detail.In chapter 3, compounds designed in chapter 2 were synthesized efficiently to afford a series of starburst triphenylamine-based organic dyes. The results of their structure-activity relationship indicated that the products bearing two diphenylamine frameworks possess excellent photochemical properties, but their HOMO/LUMO level did not fit the design requirement of organic dyes. The products having only one diphenylamine framework possessed a non-planar structure and hold the suitable HOMO/LUMO level, but their melting point was low and their fluorescence was not strong enough which made them not fit as dye for DSSCs. It suggested that the further structure modification is necessary if we want to develop them as good organic dye sensitizer.In chapter 4, some electron-withdrawing groups such as aryl methylene malononitrile, aryl methylene cyanoacetic acid, 1- indole or isophoron were introduced in the electron-donoring triphenylamine skeleton to give novel starburst triphenylamine-based D-D-π-A organic dyes. The results of their photochemical and electrochemical properties indicated that the introduction of electron-withdrawing groups afforded more smooth and directional electron flow which gave the better photoelectric property of products than the simple D-π-A organic dyes’ such as red-shifted absorption spectra, enhanced molar extinction coefficients and better thermo-stability. It means they can be developed as good organic dye sensitizer in the future.In chapter 5, the products were made into a device and assembled on a solar cell. The results of their photoelectric conversion efficiency showed that three compounds gave satisfactory result. It also showed the strong finality and good operability of the syntheses under the guidance of reasonable design and calculation.In chapter 6, we have summarized this paper.