Application Of Unsymmetrical Hemicyanine Dyes With Pyridinium Or Indolium As Acceptor And Organic Redox Couples In DSSCs

As key components of dye-sensitised cells, sensitizers and electrolytes play important roles for photovoltaic conversion.In this thesis, eleven unsymmetrical hemicyanine dyes with pyridinium unit as acceptor were designed and synthesized. The introduction of pyridinium unit into the molecular frame as acceptor instead of cyanoacrylic acid unit can effectively cause a red shift in the absorption spectrum. When such dyes were applied to DSSCs as sensitizers, higher Jsc but lower Voc were got, compared with the sensitizers with the same donor but employing cyanoacrylic acid unit as acceptor. For the device sensitized by CM104, an efficiency of7.0%(Jsc=13.4mA·cm-2, Voc=704mV, FF=74.8%) was achieved, while for the device sensitized by reference dye CMR104, the photovoltaic conversion efficiency is3.4%(Jsc=6.2mA·cm-2, Voc=730mV, FF=74.8%).Three D-A-A type unsymmetrical hemicyanine dyes, with pyridinium unit connecting with cyanoacrylic acid unit, were designed and synthesized. When these D-A-A type dyes were applied to DSSCs, it was found that the D-A-A type unsymmetrical hemicyanine dyes display wide response to solar spectrum and an efficiency as high as8.8%with liquid hybrid electrolyte was achieved for CM203.The dyes with7V-butyl-2,3,3-trimethyl-5-carboxy-indolium unit as acceptor show very strong absorption in relatively narrow spectrum range (500-660nm). For the device sensitized by CM303, an efficiency of5.0%(Jsc=12.2mA·cm-2, Voc=596mV, FF=68.9%) was achieved. When CM303was explored as a co-sensitizer in co-sensitized solar cells in combination with the other two organic dyes CMR103and HY113, much higher photocurrent and efficiency than those of individual dye sensitized cells were achieved. The co-sensitized solar cell shows a panchromatic response with high IPCE value exceeding85%in between400-700nm.A novel electrolyte was prepared by employing L-cysteine/L-ystine as redox couple. When this electrolyte applied to DSSCs, similar efficiency was achieved comparing with traditional I-/I3--based electrolyte. This novel electrolyte system contains neither iodine nor iodide, it is non-corrosive to metal current collector in large area DSSCs panel and it is critical for the commercialization and industrialization of DSSCs. The hydroquinone (HQ)/benzoquinone (BQ) redox couple was introduced to prepare both hybrid electrolyte and iodide-free electrolyte. The new hybrid system turned out to outperform the well-known I-/I3-redox system. An efficiency of8.4%was achieved under AM1.5G illumination using N719as photosensitizer, which is higher than the recorded efficiency of8.0%for the corresponding system employing a pure iodine-based electrolyte.