Performance variation from triphenylamine- to carbazole–triphenylamine–rhodaniline-3-acetic acid dyes in dye-sensitized solar cells

Organic dyes have been synthesized which contain an extra-electron donor (carbazole) and electron acceptors (rhodaniline-3-acetic acid) on triphenylamines (TPA). Photophysical, electrochemical, and theoretical computational methods have categorized these compounds. Nanocrystalline TiO2-based dye-sensitized solar cells (DSSCs) are fabricated using these dye molecules as light-harvesting sensitizers. The overall efficiency of sensitized cells has 4.64% relative to a cis-di(thiocyanato)-bis(2,2′-bipyridyl)-4,4′-dicarboxylate ruthenium (II) (N3 dye)-sensitized device (7.83%) fabricated and measured under the same conditions. Carbazole-electron donation in the dye molecules plays a key role in the increased efficiency. Two rhodaniline-3-acetic acid groups appear to help convey the charge transfer from the excited dye molecules to the conduction band of TiO2, leading to a higher efficiency of devices using such a dye. Electrochemical impedance supports this dyeʹs effect on enhancing charge transfer in TiO2 (e−). Computations on this dye compound also indicate the larger charge transfer efficiency in the electronically excited state.