Light-scattering photoanodes from double-layered mesoporous TiO 2 nanoparticles/SiO 2 nanospheres for dye-sensitized solar cells

Understanding the role of silica nanospheres with their light scattering and energy barrier properties in enhancing the photovoltaic performance of ZnO based solar cells

The present study discusses the design and development of a dye sensitized solar cell (DSSC) using a hybrid composite of ZnO nanoparticles (ZnO NP) and silica nanospheres (SiO₂ NS). A ≈22% enhancement in the overall power conversion efficiency (PCE, η) was observed for the device fabricated with a binary hybrid composite of 1 wt% SiO₂ NS and ZnO NP compared to the pristine ZnO NP device. A systematic investigation revealed the dual function of the silica nanospheres in enhancing the device efficacy compared to the bare ZnO NP based device. Sub-micron sized SiO₂ NS can boost the light harvesting efficiency of the photoanode by optical confinement, resulting in increased propagation length of the incident light by multiple internal reflections, which was confirmed by UV-Vis diffused reflectance spectroscopy. Electrochemical impedance spectroscopic (EIS) analysis showed a reduced recombination of photo-generated electrons to the I^-/I₃^- redox shuttle in the case of the composite photoanode. The higher recombination resistance (R_ct) in the case of a 1 wt% composite indicates that the SiO₂ NS serves as a partial energy barrier layer to retard the interfacial recombination (back transfer) of photo-generated electrons at the working electrode/electrolyte interface, increasing the device efficiency.

Efficient Dye-Sensitized Solar Cells Based on Nanoflower-like ZnO Photoelectrode

A photoanode material ZnO nanoflower (ZNFs) for efficient dye-sensitized solar cell (DSSC) was prepared. This unique structure can significantly increase the specific surface area and amount of light absorption, leading to a higher short-circuit current density. Furthermore, ZNFs resulted in closer spacing between the nanorods and more direct conduction paths for electrons, leading to higher open-circuit voltage. The overall promising power conversion efficiency of 5.96% was obtained with photoanodes of 8.5 μm thickness. This work shows that ZNFs is an attractive material and has good potential for application in high efficiency ZnO-based DSSCs.