A diminutive modification in arylamine electron donors: synthesis, photophysics and solvatochromic analysis - towards the understanding of dye sensitized solar cell performances

An electron rich donor moiety plays an important role in dye sensitized solar cells (DSCs). In order to attain a suitable donor moiety for DSCs, a deeper understanding of the role of a donor moiety in the dye excited state is significant. In this context, different arylamine dye-based electron donor moieties (TRA, CRA and PyRA) were successfully synthesized and well characterized using 1 H-NMR, 13 C-NMR and EI-MS spectrometry. Their photophysical properties and solvatochromic behavior were studied using UV-visible absorption, steady state and time resolved fluorescence spectroscopic techniques. The absorption of arylamine dyes is due to intramolecular charge transfer (ICT) between the donor and rhodanine-3-acetic acid via a π-bridge, which is further confirmed by DFT calculations. Lippert-Mataga analysis on the solvatochromic data implies that these molecules are more polar in the excited state, which is additional support for ICT. Furthermore, nanocrystalline TiO 2 -based dye sensitized solar cells (DSCs) were fabricated using these dyes to investigate the influence of donor moieties on their photovoltaic performance. The overall power conversion efficiencies of 2.57%, 1.68% and 1.25% were obtained for the TRA, PyRA and CRA dyes, respectively. The enhanced power conversion efficiency of TRA is due to a longer lifetime of injected electrons as demonstrated by the electrochemical impedance spectroscopy (EIS) measurements. An electron rich donor moiety plays an important role in dye sensitized solar cells (DSCs).