PHOTOSPECTROSCOPY OF I_3~-SPECIES IN DYE SOLAR CELLS (DSC) AS A TEST FOR THE SEALING AND DIFFUSION BARRIER PROPERTIES OF GLASS FRIT

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 (GF). Sintered GF layers were openly exposed to non-aqueous redox electrolyte and redox electrolyte with 1, 5 and 10 wt% H_2O in thin, encapsulated cells. The I_3~-absorbance change was monitored over 100 days. 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. Two out of the four investigated GFs were unstable when H_2O was added to the redox electrolyte. The effect of H_2O caused metal ion leaching which was determined from EDX analysis of evaporated electrolyte samples. A GF based on Bi2O3-SiO_2-B_2O_3 with low bond strength leached bismuth into electrolyte, and formed the BiI_4~- complex. A GF based on ZnO-SiO_2-Al_2O_3 also became unstable when H_2O was added to redox electrolyte. Leaching of zinc ions due to exchange with H+ resulted in the formation of a zinciodine complex 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.