Anatase TiO2 microspheres with smooth and fibrous morphology (SμS and FμS) resembling laddu and dandelion are synthesized by solvothermal and hydrothermal methods, respectively. A detailed analysis of these two microstructures using XRD, UV–vis spectroscopy, electron microscopy and surface area measurement techniques are presented. Photoanodes fabricated using these microspheres and their composites with nanoparticles (Degussa P25) are tested for photovoltaic (PV) performance using a standard Grätzel-type dye-sensitized solar cell (DSSC) configuration.
The DSSC made up of SμS and FμS microspheres exhibit an efficiency (η) of 8.4% and 6.4% respectively, in comparison to η≈7.1% for nanoparticulate P25. Further enhancement in η is realized in the composite photoanode films made of porous SμS/FμS microspheres filled with nanoparticulate P25 TiO2. High power conversion efficiency of 8.9% (for cell area of 0.5 cm2 and thickness of ~25 µm) was achieved in composite photoanode film consisting of 80 wt% SμS and 20 wt% P25. Electrochemical impedance spectroscopy studies reveal a low interfacial resistance in composite photoanodes, which is desired for efficient electron generation and transport.
Composite microspheres filled with P25 nanoparticles in their voids show enhanced efficiency than the mesoporous TiO2 microspheres. Thus, SμS-nanoparticle composite TiO2 film possesses essential attributes necessary for an efficient photoanode viz. large surface area for dye adsorption, good connectivity between nanocrystallites for the efficient electron transport, and higher scattering properties for better light harvesting efficiency.
Ilaiyaraja, P., Das, T.K., Mocherla, P.S. and Sudakar, C., 2017. Well-connected microsphere-nanoparticulate TiO 2 composites as high performance photoanode for dye sensitized solar cell. Solar Energy Materials and Solar Cells, 169, pp.86-97.
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