Degradation mechanism of ZnO-based dye-sensitized solar cells

Zinc oxide (ZnO)-based dye-sensitized solar cell was fabricated and tested under constant solar simulator illumination until the photocurrent decreased. Electrolyte and dye were studied by Fourier transform infrared and UV–vis absorption spectroscopy. Scanning electron microscopy, photoluminescence and X-ray photoelectron spectroscopy were used to study the degradation of ZnO. Secondary Ion Mass spectroscopy was used to analyze the structural change of the device during the degradation process. The degradation process of dye-sensitized solar cell is started when N3 dye slowly gets desorbed from the ZnO surface and gets incorporated into the electrolyte. Electron injection decreases with time as more dye gets desorbed. The degradation process is further accelerated when ions of Zn, O and In are diffused into the electrolyte as this process create defect vacancies on the ZnO nanorod surface. The stability of the semiconductor surface and interface between the semiconductor and dye are crucial to improve device lifetime.