Synthesis and optical identification of some modified small molecule-natural dyes for bulk heterojunction solar cells

In this study, some selected natural dyes and chromophores were derivatized in order to use in bulk-heterojunction solar cell (BHJC) applications. In particular, it was preferred some special structures which were environmentally safe to use and biodegradable. These selected structures including specific benzimidazole group, isoindigo pigment, cibalackrot dye, riboflavin vitamin, tyrian purple dye and their derivatives were synthesized and prepared for BHJCs. The first stage of this project, the structure of five above-mentioned natural materials have been modified to be compatible with BHJC systems. These modifications included some specific groups to gain some improvements into dye with basic parameters by adding special groups to improve their solubility, to shift their absorptions bathochromically, to ensure the formation of appropriate band gap. Structural characterizations were made by FT-IR, 1H-NMR, 13C-NMR and mass spectroscopy. As a result; 3 benzimidazole-containing dyes, 5 isoindigo dyes, 2 cibalackrot dyes, 2 riboflavin type dyes, and 3 tyrian purple dyes, totally, 15 novel target natural dyes have been synthesized. The second stage of the project, photophysical properties (UV-vis, fluorescence, excited state dynamics) of the substances in solutions and on thin films were investigated. Band gaps were calculated from the cyclic voltammetry (CV) measurements. Potential appliciability of the synthesized new dyes in the BHJC technologies have been discussed according to their measured optical and electrocemical properties. These novel dyes target appear to be promising for BHJC technologies. Keywords: Organic photovoltaic, small molecule Bulk heterojunction solar cell, cibalackrot, riboflavin, isoindigo, tyrian purple, benzimidazole