This study investigated the degradation of a DSSC module consisting of 22 unit cells for thermal stability. A 1000-h thermal stability test was conducted at 85 degrees C, after which the cells maintained ca. 73.5% of their initial overall power conversion efficiency (eta). The degradation was also systematically investigated using Raman spectroscopy. The results revealed that loss of the overall power conversion efficiency was due to (i) desorption of the Z-907 dye from the TiO2 electrode, and (ii) dissociation of SCN- from the Z-907 dye. In addition, analyses of 2D Raman mapping determined the following factors after the thermal stability test: (i) the defect vacancy of Z-907 on the TiO2 surface in the cell, (ii) the leakage of the desorbed Z-907 into the sealing material from the cell, and (iii) the dissociation of SCN- ligand throughout the cell. (C) 2016 Elsevier Ltd. All rights reserved.