A five-fold efficiency enhancement in dye sensitized solar cells fabricated with AlCl₃ treated, SnO₂ nanoparticle/nanofibre/nanoparticle triple layered photoanode

Abstract: The use of electrospun nanofibre (NF) membrane of SnO₂ toward the efficiency enhancement in dye sensitized solar cells (DSSCs) with a triple layered, AlCl₃ treated SnO₂-based photoanode is presented. The performance of DSSCs fabricated with SnO₂ nanoparticle (NP)-based photoanode is compared with that of DSSCs made with a novel triple layered SnO₂ photoanode of configuration FTO/NP/NF/NP. Thickness of the NF membrane is optimized to achieve the highest solar cell performance. Solar cells made with single layer SnO₂ NP photoanode sensitized either by Eosin-Y dye or Indoline dye showed efficiencies of 0.3% and 2.02%, respectively, under the irradiance of 100 mW cm⁻² (AM 1.5), while the corresponding devices with AlCl₃-treated, triple layered photoanode showed efficiencies of 1.55 and 2.77%, respectively, under the same illumination. Accordingly, more than five-fold enhancement in overall efficiency is achieved in DSSCs by using this novel SnO₂-based photoanode with the optimized thickness of the SnO₂ nanofibre membrane and sensitized with Eosin-Y dye. Scanning electron microscopic studies revealed that the SnO₂ nanofibre membrane consists of an interconnected network-like structure formed by the SnO₂ nanofibres. Electrochemical impedance spectroscopy measurements on DSSCs made with these two types of photoanodes reveals that the series resistance of the DSSC made with the novel NP/NF/NP triple layered photoanode is significantly reduced. The observed higher electron lifetime determined from Bode plots shows that electron recombination is lower in the DSSCs made with the triple layered photoanode. Improved light harvesting by multiple scattering effects within the triple layered photoanode structure and the suppression of the electron recombination by Al₂O₃ sub-nanometer-sized coating around SnO₂ appear to be the major factors for the enhancement in photo current density and efficiency. Graphicasl Abstract: [Figure not available: see fulltext.].