The effect of the presence of 5CB liquid crystal molecules in the electrolyte on the current–voltage parameters of the DSSC cell

This work experimentally compares the operating characteristics of dye-sensitized solar cells (DSSCs) with cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II) (N3) dye for two iodide/tri-iodide liquid electrolyte (AN-50) variants: (a) classic AN-50 iodide electrolyte, and (b) AN-50 modified with 4-n-pentyl-4’-cyanobiphenyl (5CB) liquid crystal (LC) additive (10% ) at an operating temperature of 300–303 K. The aim was to determine the effect of the 5CB additive on the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), power of the real cell (Pmax) parameters and resistive loss indices (Rs—Joule effect losses; Rsh—shunt resistance) and to formulate mechanistic conclusions (ion transport vs. recombination/interface). For each sample, a quasi-static measurement run was performed under constant illumination (116 klx) and controlled sample temperature. Load conditions were varied over time (sweep), while the sample voltage V(t) and current I(t) were recorded. The current–voltage (I–V) and power–voltage (P–V) characteristics were determined from the (V, I) pairs after their time synchronization. The introduction of 5CB into the AN-50 electrolyte affects the balance between ion transport/diffusion of redox couples I⁻/I₃⁻ and recombination losses at the photoanode–electrolyte interface. The literature shows that LC used as electrolyte additives can increase the "transmission paths" of redox couples, which favors an increase in Isc; however, the effect is concentration-dependent and can be reversed if the additive content is too high. In the tested samples, higher Voc and Isc were observed on average compared to the single control, with a simultaneous lower FF. This combination is consistent with the hypothesis of (a) partial improvement in generation/transport (Isc), but (b) increased resistive-transport losses or changes in electrode kinetics that reduce FF. Due to the single control and different measurement dates, this conclusion should be considered preliminary and requires confirmation by measurements under identical conditions.