Glass Frit Dissolution Influenced by Material Composition and the Water Content in Iodide/Triiodide Electrolyte of Dye-Sensitized Solar Cells

摘要

To ensure long-term stable dye-sensitized solar cells (DSCs) and modules, a hermetic sealing is required. This research investigates the chemical stability of I~-/I_3~- redox electrolyte and four different glass frits (GFs). Sintered GF layers were openly exposed to nonaqueous redox electrolyte and redox electrolyte with 1, 5, and 10 wt% H_2O in thin, encapsulated cells. The change in I_3~-absorbance was assigned to a reaction between the GF and I~-/I_3~- electrolyte and was used to evaluate the chemical stability of the different GFs. The I_3~- absorbance change was monitored over 100 days. Two out of the four GFs were unstable when H_2O was added to the redox electrolyte. The H_2O caused metal ion leaching which was determined from EDX analysis of the inorganic remains of electrolyte samples. A GF based on Bi_2O_3-SiO_2-B_2O_3 with low bond strength leached bismuth into electrolyte and formed the BiI_4~- complex. A ZnO-SiO_2-Al_2O_3-based GF also became unstable when H_2O was added to the redox electrolyte. Leaching of zinc ions due to exchange with H~+ resulted in the formation of a zinc-iodine compound which caused I_3~- depletion. By applying the test design to different types of GFs, the material suitability in the DSC working environment was investigated.