Bile Acid Derivatives As Novel Co-adsorbents for Enhanced Performance of Blue Dye-Sensitized Solar Cells

Diketopyrrolopyrrole-based blue dyes in dye-sensitized solar cells (DSCs) exhibit promise for building-integrated photovoltaics, but their efficiency is compromised by dye aggregation-induced charge recombination. Novel bile acid derivative co-adsorbents featuring bulky hydrophobic substituents at the 3-β position were synthesized to address this challenge. These molecules, designed to modulate intermolecular electronic interactions, effectively altered the TiO2 surface coverage dynamics, as evidenced by UV-Vis spectroscopy and dye-loading kinetics. Systematic variation of hydrophilic substituents revealed structure-function relationships in dye separation efficacy. Devices incorporating these co-adsorbers achieved power conversion efficiencies (PCE) of 7.6%, surpassing reference devices (5.2%) and those using conventional chenodeoxycholic acid co-adsorbers (6.4%). The optimized devices exhibited a 30% increase in short-circuit current density, 30 mV enhancement in open-circuit voltage, and 60% peak external quantum efficiency at 550 nm. Time-resolved photoluminescence spectroscopy confirmed suppressed non-radiative recombination, while transient absorption spectroscopy revealed accelerated electron injection rates from 6.4 ps to 4.6 ps. Electrochemical impedance spectroscopy elucidated the mechanism of reduced interfacial recombination. These findings present a molecular engineering strategy for mitigating lateral charge transfer in planar dye systems, advancing semi-transparent hybrid photovoltaics.