Synthsis And Characterization Of New Organic Dyes For Dye-sensitized Solar Cells

Dye-Sensitized Nanocrystalline Solar Cells（DSSCs） are very prospectivecleaning devices for the conversion of solar energy into electricity. As the core of thedye-sensitized solar cells （DSSCs）, dye is the most important parts for DSSCs to gethigher efficiency. It is noted that polypyridyl ruthenium dyes showed higherefficiency which was near to12%so far. In view of the limited ruthenium resourceand the heavy-metal toxicity, metal-free organic dyes with high molar extinctioncoefficient have attracted considerable attention owing to their low-cost and goodflexibility in molecular tailoring in recent years.Most people modify the metal-free organic dyes by changing donors and π-conjugated units now. But the receptor units changed little which was mainlycyanoacetic acid or Rhodanine-N-acetic acid. We prepared several D-π-A organicdyes possessing different receptors and π-conjugated linkers and the dyes-sensitizeddevices were also characterized. The main contents are following:（1） We have synthesized several bidentate electron-acceptor dyes （ZH-1, ZH-2and ZH-3） by incorporating different π-conjugated linkers such as double bond、furan, thiophenein combination with the dihexyloxy-substituted triphenylaminedonor and malonic acid acceptor. The absorption and emission spectra of the dyeswere recorded in CHCl₃; it is found that the absorption and emission maximum werebathochromic-shift with the electron donor ability of π-conjugated linkers.The performances of the dyes-sensitized devices indicate that the maximumIPCE of these three dyes exceed80%, and the efficiencies are between3.0%and4.5%, and the short circuit current are increased and the corresponding deviceefficiency were improved with the electron-donating ability of aromatic heteroatom.（2） ZH-4, ZH-5and ZH-6were synthesized by incorporatingdihexyloxy-substituted triphenylamine donor, different π-conjugated linkers such asdouble bond、furan, thiophenein and diethyl malonate acceptor, and we introduceda new acceptor（-CN）. And the absorption and emission spectra of these dyes were recorded in CHCl₃;it is found that the absorption and emission maximum werebathochromic-shift with the electron-donating ability of π-conjugated linkers.The performances of the dyes-sensitized devices indicate that the efficiencies ofthese three dyes are between3.3%and4.5%. Furthermore we find broaderabsorption spectra, lager IPCE, bigger short circuit, smaller open-circuit voltage andhigher efficiencies of these dyes than the ones without cyanogroup.（3） Three new dyes ZH-7, ZH-8and ZH-9with two cyanogroup whoseacceptors were ethyl cynaoacetate were synthesized. Linking one more cyanogroupto the acceptor part of ZH-7, ZH-8and ZH-9dyes further extends the absorptionregion with red shifts about100nm. The absorption spectra indicated that theintroduction of another cyanogroup at acceptor is good to red-shift the longestwavelength and increase the corresponding molar extinction coefficient. But theintroduction of another cyanogroup at acceptor makes the LUMO of dyes decreasesharply and results in a lower performance.