Application of deep eutectic solvent from phenol and choline chloride in electrolyte to improve stability performance in dye-sensitized solar cells

Abstract In this study, we aim to develop an efficient, eco-friendly and cost-effective electrolyte solvent mixture for Dye-sensitized Solar Cells (DSCs) by using a deep eutectic solvent (DES). A high-purity choline chloride–phenol DES was synthesized and characterized by Fourier-transform infrared and nuclear magnetic resonance spectroscopy; thermogravimetric analysis and differential scanning calorimetry. The resulting product was mixed with acetonitrile, a typical volatile electrolyte solvent, at various ratios for use as electrolyte in DSCs. The photovoltaic parameters ( J sc , V oc , fill factor, efficiency) of these DSC devices were monitored to investigate their long-term performance. The performance of DES-added cells was initially less efficient, but more stable after more than 1000 h, compared to that of the DES-free cells. DES helped to stabilize and improve the photovoltaic performance of DSCs, particularly the short circuit current, due to the effect of the choline and phenol groups of DES binding on the TiO 2 surface, as shown by the density functional theory (DFT) calculation. The optimal results were achieved with electrolyte containing 20% DES (efficiency = 6.9% with stable performance for more than 1000 h).