Conductivity and Thermal Properties of PAN Based Polymer Electrolytes for Possible Application in Photo Electrochemical Solar Cells

Abstract

Two gel or quasi-solid-state electrolyte complexes based on PAN (polyacrylonitrile) host polymer and salts Hex4NI (tetrahexylammonium iodide), MgI2, LiI were prepared by incorporating plasticizers EC (ethylene carbonate) and PC (propylene carbonate). These are: PAN/EC/PC/I2/Hex4NI:MgI2 and PAN/EC/PC/I2/Hex4NI:LiI. A clear glass transition was observed around -100 ° C for all the electrolyte complexes. In the PAN/EC/PC/I2/Hex4NI:MgI2 system, a decrease in conductivity was observed with the addition of MgI2 and the electrolyte with Hex4NI alone as the iodide salt gave the maximum ionic conductivity of 2.51 × 10 -3 Scm -1 at 25 ° C. In the PAN/EC/PC/I2/Hex4NI:LiI system, an increase in conductivity was observed with the addition of LiI. Consequently the electrolyte with LiI as the only iodide salt gave the maximum ionic conductivity of 3.14 × 10 -3 Scm -1 at 25 ° C. The diffusion coefficient (D), the mobility (μ) and the density of charge carriers (n) in the electrolytes were calculated using complex impedance data and equations obtained for dielectric loss tangent. The measured data for dielectric loss tangent were fitted to the model equation. Calculated, n, μ and D values are around ~10 24 m -3 , ~10 -7 m 2 V -1 s -1 and ~10 -9 m 2 s -1 respectively for the two electrolyte systems. This type of iodide ion conducting electrolytes could be suitable materials for PEC (photo electrochemical) solar cells.