Organic D-Ï€-A Sensitizers With Different Pyridiniums As Acceptor Group For Dye-sensitized S0Lar Cells

Due to the advantage of low cost and high efficiency, dye-sensitized solar cells (DSSCs) have achieved much attention from all over the world. As the key component of DSSCs, the sensitizers play an important role in the performance of DSSCs by transforming the photons to electrons. Besides, a great improvement have been obtained by the metal-free organic dyes because of high molar extinction coefficient, ease of tunable molecular structure and low cost.Three metal-free organic dyes with TPA or phenothiazine as donor group and two pyridinium (m-carboxylpyridinium and m-carboxymethylpyridinium) as the acceptor and anchoring group were designed and synthesized for DSSCs. In this paper, due to the good electron withdrawing ability and electron injection ablility of pyridinium, different types of pyridinium as acceptor group were introduced into the molecules of these dyes instead of traditional acceptor group (cyano acrylic acid). In order to study the effect of different types of acceptor groups on the properties of photophysical, electrochemical and photovoltaic of dyes, UV-visible absorption spectra, density functional theory calculations, J-V curves and electrochemical impedance spectroscopy were systematically investigated. In addition, because the dyes are easy to aggregate on the surface of TiO2, the CDCA are added to restrain this phenomenon.In this paper, it is easy to find that the ionization of pyridine dyes is favorable to enhance the electron withdrawing ability, reduce the band gap, broaden the absorption spectra and improve the Jsc. Besides, the Voc (except the TJ101R), Jsc and efficiency values are greatly improved with the addition of CDCA by reducing the aggregation of dyes on the surface of TiO2. The devices sensitized by dye TJ101achieved the best conversion efficiency of5.4%(Jsc=10.8mA·cm2, Voc=680mV, FF=74.2%) under AM1.5irradiation(100mW cm-2). In contrast, the devices based on dye TJ101R with3-carboxylpyridine as the acceptor obtain only an efficiency of4.0%(Jsc=10.8mA·cm-2, Voc=680mV, FF=74.2%).