Simple metal-free dyes derived from fluorene for visually transparent solar cells: A comparative study of different anchoring groups and electrolytes

We present a straightforward synthesis of UV-harvesting dyes featuring a fluorene donor with different anchoring groups, such as cyano acetic acid, amino benzoic acid, and 2-methyl-quinoline-6-carboxylic acid (designated as FCA, FAB, and FQA, respectively). We comprehensively investigate the spectroscopic, electrochemical and colorific properties of these dyes and evaluate their suitability as photosenstizers in visually transparent and colorless dye-sensitized solar cells (DSSCs). FCA and FQA possessing planar geometries exhibit remarkably efficient collection of UV photons, leading to excellent power-conversion-efficiencies (PCEs) under UVA radiation. Furthermore, we explore the incorporation of the binary redox couple, (I−,Br−)/(I3−,I2Br−), to enhance the ability to transmit visible light, positively impacting their color rendering properties, while preserving their light harvesting capacities. •Fluorene-based dyes with different anchoring groups are easily synthesized.•UV-absorbing dyes can be used as effective photosensitizers for UV-selective DSSCs.•Binary redox couple improves visible light transmission and enhances color rendering properties of the solar cells.