Synthesis And Properties Of Organic Photovoltaic Materials Based On Quinoxaline Structural Unit

The research progress of the organic small molecule solar cells were reviewed inthis dissertation. The absorption spectra, solubility and hole mobility of organicphotovoltaic donor materials are the major factors to affect the power conversionefficiency (PCE) of organic solar cells. In order to improve the charge carrier mobilityand broaden the absorption spectra of small molecular material, Herein, three kinds oforganic small molecular photovoltaic materials had been synthesized, such asstar-shaped D4-A, narrow band gap of the star-shaped D4-A and dual acceptor ofstar-shaped D(AD)2structural units based on quinoxaline unit. The structures of thesematerials were characterized by1H-NMR,13C NMR and Time-of-fight mass spectra.The photophysical, thermal stability, electrochemical and photovoltaic properties ofthese materials had been investigated by UV-Vis spectra (UV), thermogravimetricanalysis (TGA) and Cyclic Voltammetry (CV). In addition, the photovoltaicperformances of organic solar cells based on these small molecules were fabricated.The key study results are listed below:1. There are four organic photovoltaic materials with star-shaped D4-A systemsbased on quinoxaline had been designed and synthesized, the effects of differentdonors upon the photophysical, electrochemical and photovoltaic properties of themolecules were studied. With the number of strong donor units increasing, the UV-visabsorption presents red-shift, and the power conversion effciency was improvedsignificantly. Under the simulated sunlight illumination of AM1.5,100mW/cm2, theenergy conversion efficiency (PCE) was achieved0.37%in the device.2. There are six organic photovoltaic materials with star-shaped D4-A systemsorganic small molecular photovoltaic materials had been designed and synthesized,the effects of different numbers of thiophene units upon the photophysical,electrochemical and photovoltaic properties of the molecules were studied. Withincreasing the conjugated length and thiophene units in the materials, the bandgap ofmaterials decrease. We found that the materials with four thiophene units showed abetter photovoltaic performance than that of the containing two thiophene units. Theenergy conversion efficiency (PCE) was achieved1.11%in the device.3. There are three organic small molecular photovoltaic materials with an dualacceptor of star-shaped D(AD)2systems had been designed and synthesized, which containing different electron transport capacity of carbazole, fluorene anddibenzothiophene derivatives as a bridge linker, the effects of carbazole, fluorene anddifferent linkers upon the photophysical, electrochemical and photovoltaic propertiesof the materials were studied. With increasing the electronic transmission capacity ofcarbazole, fluorene and dibenzothiophene derivatives, the materials showed a broaderabsorption spectrum and a lower bandgap. The energy conversion efficiency (PCE)was achieved0.23%in the device.The results of photovoltaic performances of organic solar cells based on thesematerials show that the molecular design is crucial to achieve organic small molecularphotovoltaic materials with a good stability and a high photovoltaic efficiency. Thephotovoltaic properties of organic solar cells can be optimized by tuning themolecular structure. This study is significant to further study on influence ofquinoxaline with functionalized groups on the photovoltaic properties of organicsmall molecular photovoltaic materials and improve carrier-transporting property andphotovoltaic efficiency, as well as achieve some novel of organic small molecularphotovoltaic materials.