Stability improvement by incorporating poly(ε-caprolactone) in dimethylformamide-potassium iodide liquid electrolyte for dye-sensitized solar cell

Abstract

Poly(e-caprolactone) (PCL) was chosen as a gelator for dimethylformamide (DMF)-potassium iodide (KI) liquid electrolyte. The mass fraction of PCL, WPCL was varied from 0.1 to 0.6. Evidence of interaction between PCL, DMF, and KI has been obtained from the FTIR studies. Competition between PCL and DMF on associating with the cation of salt was estimated by fitting the ν(C=O) mode (1500–1800 cm−1). PCL in DMF-KI electrolyte promotes salt dissociation but adversely increases the electrolyte viscosity. From the impedance measurement, PCL causes greater reduction in ion mobility, μ than increment in ion density, n. Consequently, conductivity of DMF-KI electrolyte decreases with PCL. DSSCs were assembled with DMF-KI liquid electrolyte and PCL-DMF-KI gel electrolyte. DSSC with liquid electrolyte shows efficiency of 12.40 ± 0.05% with short-circuit current density, Jsc of 33.31 ± 0.25 mA cm−2. PCL decreases the efficiency and Jsc of DSSC from 12.40 ± 0.05% to 6.99 ± 0.04% and 33.31 ± 0.25 to 14.05 ± 0.06 mA cm−2, respectively, but it improves the stability performance of DSSC. Improved stability is due to the suppression of electrolyte evaporation and degradation of Pt counter electrode by the PCL.