The Design, Synthesis And Optoelectronic Properties Of Novel Conjugated Polymers And Conjugated Oligomers

With the growth of population and the development of industry, the human requirement for energy is growing. In accordance with the current rate of petrochemical resources’ consumption, the main energy- fossil resources can only be maintained for decades to use. In order to solve the contradiction between development and energy demand, the search for new, green, green, renewable energy has become an urgent need to solve the world’s problems. Human use solar energy very eary and pay more attention to the solar energy now because of the inexhaustible feature. The most important way to effective use of solar energy is converting the solar energy directly into the electricity. But now the low efficiency and high cost limit the development of solar energy utilization in the industry. Compared with conventional inorganic silicon solar cells, organic solar cells(organic solar cell, OSC) has a lightweight, low-cost, flexible, enabling the printing process(roll-to-roll printing) and large and widespread concern. Currently, the literature of organic photoelectric conversion efficiency of solar cells has been more than 10%, but to really achieve large-scale commercial applications, there are many problems need to solve. Efficiency and life issues of organic solar cells, in addition to process optimization and innovation, more rely on the synthesis of new materials and design.Polymer near-infrared(NIR) detectors is another important branch of organic photoelectric. Compared to traditional inorganic near infrared detector material(silicon, indium gallium arsenide, etc.), polymer near-infrared detectors have attracted much attention, due to its low-cost, easy processing, a wide range of light response, high sensitivity, wide range detection. It has great practical value in biosensing night imaging, environmental monitoring and so on. Design and synthesis of new polymer materials is a major breakthrough in the near-infrared in this field.In this thesis, we have designed and synthesized several electron-deficient structure units, such as pyridine thiadiazole unit, fluoro benzothiadiazole. The electron-deficient structure units, which have chemically selective priority, have applied to design and synthesis regularity materials to obtain narrow band gap polymers. Those low band gap polymers were characterized and analysised energy conversion efficiency.In the second chapter, a series of 9-methyl fluorine based oligomers have been synthesis by Suzuki coupling. We have optimized this structure by introducing different electron withdrawing units, including pyridinethiadiazole, fluoro benzothiadiazole, benzothiadiazole. The results show that the introductionof stronger acceptor greatly increases the HOMO level and red-shiftted significantly.In the third chapter, a series of donor–acceptor type of π-conjugated oligomers based on dithieno[3,2-b;2′,3′-d]silole as the electron donor and 2,1,3-benzothiadiazole as the electron acceptor were designed and synthesized. It was found that the elongation of the molecular lengths of the chromophores can significantly influence the thermal properties, UV-vis absorption, electrochemical properties, and photovoltaic performances of fabricated organic solar cells. The higher molecular weight chromophore exhibited a narrower band gap compared to lower molecular weight counterparts. Solution processed bulk-heterojunction organic solar cells were fabricated with the inverted device structure of ITO/PFN-OX/oligomer:PCBM/Mo O3/Al, in which the best device performance was achieved with a power conversion efficiency of 1.12%. These results indicated that the elongation of the molecular length of π-conjugated small-molecules can be an effective strategy for improving the organic photovoltaic performance of narrow band-gap chromophores.In the fourth chapter, we use the precursor ADA of the third chapter as a new acceptor to build regular D2-A-D1-A terpolymers with different donor through stille coupling. Compared the conventional D-A, the D2-A-D1-A terpolymers have shown better fine-tuning ability in energy levels and absorption spectrum. D2 and D1 can achieve a better balance between the solubility and π-π stacking. The efficiency of PBDT-O-ADA obtained 4.1%, which better than the same unit D-A polymer.In the fifth chapter, we combine the material design concept weaker donor strong acceptor to designed a series of new D2-A-D1-A, which the D1 is a moderate donor benzodithiophene and A is a strong acceptor pyridinethiadiazole. The highest effiency was close to 5.0%.The end, we develop a new unit: 5-fluorobenzoselenadiazole. We use the new unit to building the D2-A-D1-A terpolymers. These polymers have shown fair performance in their solar cell devices. The photoresponse of CDTPSE can reach 1100 nm, which have hunge pontential in terms of organic NIR detectors.