Novel Method to Improve Performance of Dye-sensitized Solar Cells Based on Quasi-solid Gel-Polymer Electrolytes

Abstract

This manuscript is concerned with the successful attempts we have made to circumvent the problems associated with I−/I3− redox couple-containing, ethylene carbonate (EC) and propylene carbonate (PC)-plasticized, polyacrylonitrile (PAN)-based gel polymer electrolyte used in dye-sensitized solar cells (DSCs). We identify the poor pore filling by a quasi-solid to be the major obstacle impeding the performance of such DSCs. In the systematic study reported here, we have prepared four types of DSCs, (a) with only the redox couple containing plasticized gel-polymer electrolyte sandwiched between two electrodes, (b) same electrolyte but hot-pressed for the gel to better penetrate into the pores of the dyed, interconnected, nanocrystalline TiO2 matrix, (c) pores filled with the usual liquid electrolyte (acetonitrile containing I−/I3− redox couple) but reducing the problems of volatile liquids by sealing the pores containing the liquid electrolyte by pressed PAN gel electrolyte and (d) DSC with the usual liquid electrolyte. The efficiencies of the DSCs from (a) to (d) are 4.1%, 5.2%, 8.4% and 9.8%, respectively. The enhanced efficiencies in this order are clearly due to significant enhancements in the short-circuit photocurrent densities of the cells. Our novel invention of (c) cells overcome the problems associated with DSCs based on quasi-solid state gel polymer electrolytes as well as those based on usual less viscous liquid electrolytes. The efficiencies of such former cells (c) are very close to those of the latter cells (d). This simple method can be universally adopted for all quasi-solid-state electrolyte-based DSCs in order to improve their performance and durability.