Structural effect of Low-dimensional carbon nanostructures on Long-term stability of dye sensitized solar cells

• DOI: 10.1016/j.cej.2022.135037
• Publication Date: 2022-02-04T16:49:27Z
• Authors: Rusoma Akilimali; Gurpreet Singh Se...; Mahyar Mohammadne...; Ibrahima Ka; Zhiming M. Wang; Gregory P. Lopinski; Haiguang Zhao; Federico Rosei
• Keywords: two-dimensional nanocarbons; hybrid composite; long-term stability; carrier dynamics; 02 engineering and technology; dye-sensitized solar cells; 0210 nano-technology; 7. Clean energy

A major challenge in upscaling and commercializing dye-sensitized solar cells (DSSC) is to simultaneously rely on a robust photoconversion efficiency (PCE) along with long-term device stability. Two-dimensional (2D) nanocarbon materials are known to improve the PCE and stability of devices made of hybrid nanocomposite photoanodes. However, there is inadequate knowledge on how the morphology of 2D nanocarbon materials plays an important role in improving photovoltaic (PV) performance and stability. Here we report the comparative effect on the PV performance and the long-term stability of DSSCs made of optimal loadings of few-layer graphene (FLG) flakes and graphene nanoribbons (GNR) into the mesoporous TiO₂ active layer. DSSCs were fabricated by using standard nanocrystalline TiO₂, GNR-TiO₂ and FLG-TiO₂ hybrid mesoporous films as anodes and subjected to continuous visible light irradiation to monitor their long-term stability. Results show that the optimized incorporation of GNR (0.005 wt%) and FLG (0.010 wt%) in the mesoporous TiO₂ active layer enhances the PCE by 34% and 21% compared to pristine TiO₂, respectively. Moreover, the operational stability of hybrid devices shows a 51.6% (for GNR-TiO₂) and a 10% (for FLG-TiO₂) sustained higher PCE than the device based on bare TiO₂, after 273 h of continuous one sunlight soaking. The electrochemical impedance spectroscopy (EIS) and transient photovoltage decay were studied to investigate how GNR strikingly reduces degradation of device performance as compared to its counterpart FLG-TiO₂ and TiO₂ based cells. This significant enhancement can be attributed to the structural modifications induced by GNR within the TiO₂ photoanode, which improves the electron lifetime and reduces non-radiative carrier recombination.