Role of Carbon Nanotubes to Enhance the Long-Term Stability of Dye-Sensitized Solar Cells

Improving the long-term stability of dye-sensitized solar cells (DSSCs) is a critical challenge which affects both their technical viability and future large-scale commercialization. Here, we investigate the role of multiwall carbon nanotubes (MWCNTs) in improving the long-term stability of DSSCs by comparing the performance of two series of devices made of (i) bare nanocrystalline TiO2 and (ii) MWCNTs-TiO2 composite anode, which are exposed to continuous simulated sunlight, indoor and ultraviolet (UV) light irradiation. The DSSCs based on the composite anode showed approximately 3 times longer stability compared with the standard device. To understand the degradation mechanisms that underpin these changes in device performance, both devices were characterized using various techniques. The results indicate that the MWCNTs can act as a conductive support, reinforcing the TiO2 nanoparticles’ matrix and offering a directional path to the photoinjected electrons, which enhances electron lifetime and reduces the carrier recombination rate. UV stability measurements demonstrated that MWCNTs can partially absorb and act as a blocking agent for UV light, thereby preventing degradation. The Raman spectra showed that dye desorption was decreased by the addition of MWCNTs. Our results provide a fundamental understanding of photoanode degradation mechanisms under illumination and offer a simple, low-cost, and large-area scalable approach to fabricate solar-energy-conversion devices with long-term stability.