Investigation of the mixed cation effect and the irradiance level dependence on the efficiency of dye‑sensitized solar cells

Abstract

The development of photoelectrochemical energy conversion devices holds immense significance in addressing the escalating demand for renewable and environmentally benign energy. By harnessing the synergistic effects of salt mixtures that encompass both large and small counter ions, notable advancements in dye-sensitized solar cell (DSSC) performance have been realized. The investigated DSSCs with a novel organic electrolyte complex that contains LiI and (tetrahexylammonium) Hex4NI exhibited significant efficiency enhancement compared to that of their individual salt end components. The ionic conductivity variations and frequency-dependent AC conductivity in the electrolyte and dielectric properties were analyzed using complex impedance data. The conductivity in the electrolyte at room temperature is 11.44 mS cm−1. The investigated DSSCs are comprised of improved TiO2 multilayer photoelectrodes and Pt counter electrodes. Under an irradiance of 1000 W m−2, the energy conversion efficiency of the mixed salt system reached 8.37%, marking an impressive enhancement of 86.83% and 76.21% compared to the Hex4NI and LiI-based single salt counterparts, respectively. Additionally, an impressive efficiency of 10.57% is shown when the light intensity drops to 400 W m−2. The cells exhibited commendable short-term stability, likely attributed to the elimination of volatile solvents in the electrolyte. This study underscores the pivotal role played by mixed counter ions in the electrolyte, as they elicit synergistic effects that amplify DSSC performance enhancements, effectively overshadowing the effects imposed by conductivity variation.