An efficient and nonflammable organic phosphate electrolyte for dye-sensitized solar cells

Abstract

A new fire-retardant, diethyl ethyl phosphate (DEEP), was tested as a nonflammable electrolyte solvent for dye-sensitized solar cells (DSSCs). Electrochemical measurements demonstrated that the DEEP electrolyte has a wide potential window (>5 V), sufficient ionic conductivity (3.5 × 10⁻³ S cm⁻¹ at 25 °C), and electrochemical activity for the $I^{ - } /I_{3}^{ - }$ redox couple. The DEEP-based DSSCs exhibited an open circuit voltage of 0.72 V, short circuit photocurrent of 10.45 mA cm⁻², and a light-to-electricity conversion efficiency of 4.53%, which are almost the same as those observed from the DSSCs using currently optimized organic carbonate electrolytes. Meanwhile, the long-term stability of the DSSCs was greatly improved with the use of the DEEP electrolyte, showing a potential application of this new electrolyte for the construction of efficient, stable, and nonflammable DSSCs.