Synthesis Of Arylamine-based D-A-π-A Organic Sensitizers And Performance Studies

Known as one of the third-generation photovoltaics, dye-sensitized solar cell (DSSC) has attracted extensive attention of the researchers from all over the world for its significant advantages such as relatively high efficiency, low cost and environmental-friendly characters. It is of great importance for the industrialization of DSSCs to improve the photovoltaic conversion efficiency and stability of devices. As the antenna to capture photons, the sensitizer plays a vital role on the photovaltic conversion efficiency of DSSCs. In this thesis, three series of D-A-π-A dyes (including ID (isoindigo), BT (5,6-bis-octyloxy-benzo[2,1,3]thiadiazole) and DT (2,3-diphenylpyrido[3,4-b]pyrazine) series) have been designed and synthesized via structural modifications on donor, auxiliary acceptor,π-linker and acceptor moieties. The performance of these dyes has been systermatically studied through photophysical and electrochemical measurements, as well as their photovoltaic performance.In the first chapter, the components and working principles of DSSCs are introduced. Research progress on semiconductor photoanodes, electrolytes, counter electrodes and especially the organic sensitizers in recent years is reviewed. Then the research strategy of this thesis is presented.In the second chapter, a series of ID dyes, with diphenylamine thiophene as the electron donor, isoindigo as the auxiliary acceptor, benzene/thiophene/furan as the π-linker and cyanoacrylic acid as the anchoring group has been designed and synthesized. This series of dyes has a very wide absorption band extending to NIR region but lower molar extinction coefficient, leading to a limitation on the conversion efficiency of DSSCs. Electrolytes with different components were applied to DSSCs to study their effect on photovoltaic performance. After electrolyte optimization, the highest photoelectric conversion efficiency of4.47%has been reached (Jsc=10.93mA cm-2, Voc=562mV, ff=0.728) by IDB-based DSSCs.In the third chapter, a series of BT dyes, with5,6-bis-octyloxy-benzo[2,1,3]thiadiazole as the auxiliary acceptor, thiophene as the π-linker and rhodanine as the anchoring group was designed and synthesized. Three different donors of triphenylamine, octyloxy-substituted triphenylamine and diphenylamine thiophene were introduced and it is found that BT2and BT3with more electron-donating donors had a bigger bathochromic-shift than BT1. DSSCs based on cobalt electrolyte had higher overall efficiency than that of iodine electrolyte. BTl-based DSSCs achieved the highest efficiency in both electrolytes (iodine electrolyte, Jsc=11.36mA/cm2, Voc=687mV,ff=0.714, η=5.58%; cobalt electrolyte, Jsc=13.27mA/cm2, Voc=737mV,ff=0.684, η=6.69%).In the fourth chapter, a series of DT dyes, with2,3-diphenylpyrido[3,4-b]pyrazine as the auxiliary acceptor, thiophene as the π-linker and cyanoacrylic acid as the anchoring group were designed and synthesized, including ID1, ID2with bulky donors and ID3, ED4with small donors. Research data show that the bulky dyes DT1and DT2have advantages of broadening the absorption spectrum and inhibiting the dye aggregation as well as charge recombination. Besides, enlarging the size and increasing the number of long alkyl chain are advantageous to the cobalt electrolyte to improve the overall performance of DSSCs rather than iodine electrolyte. DT1-based DSSCs achieved a highest conversion efficiency of9.52%(Jsc=17.86mA/cm2, Voc=812mV,ff=0.66).