Band‐Edge Engineered Hybrid Structures for Dye‐Sensitized Solar Cells Based on SnO2 Nanowires

In this report, we show for the first time that SnO₂ nanowire based dye sensitized solar cells exhibit an open circuit voltage of 560 mV, which is 200 mV higher than that using SnO₂ nanoparticle based cells. This is attributed to the more negative flat band potential of nanowires compared to the nanoparticles as determined by open circuit photo voltage measurements made at high light intensities. The nanowires were employed in hybrid structures consisting of highly interconnected SnO₂ nanowire matrix coated with TiO₂ nanoparticles, which showed an open circuit voltage of 720 mV and an efficiency of 4.1% compared to 2.1% obtained with pure SnO₂ nanowire matrix. The electron transport time constants for SnO₂ nanowire matrix were an order of magnitude lower and the recombination time constants are about 100 times higher than that of TiO₂ nanoparticles. The higher efficiency observed for DSSCs based on hybrid structure is attributed to the band edge positions of SnO₂ relative to that of TiO₂ and faster electron transport in SnO₂ nanowires.