Studies on new natural dye sensitizers from Indigofera tinctoria in dye-sensitized solar cells

Abstract Natural dye sensitizers are extracted from the leaves of indigo containing plant, Indigofera tinctoria by diverse extraction methods and assessed for the first time in a Dye-sensitized solar cell (DSSC). Simple cold extraction and soxhlet extraction techniques were employed for extracting the dyes from the dried leaves. A considerable yield of indigo was obtained by fermentation of fresh leaves followed by alkaline treatment and air oxidation. Acidification has been carried out for enhancing the stability of the dyes. The sensitizers were characterized by FT-IR, UV–visible spectroscopy and cyclic voltammetry while the fabricated DSSCs were evaluated in terms of their photovoltaic performances and electrochemical interphase charge transfer. Theoretical molecular modeling of the indigo molecule has been performed, and its UV/Vis, and IR spectra are simulated using Gaussian 09 suite of software. The maximum power conversion efficiency of 0.114% was obtained for DSSC sensitized with cold methanolic extract of dried leaves while the efficiency of 0.022% was recorded for the acidified crude indigo based DSSC.