RESUMO
The effect of the presence of a photonic crystal on the optical absorption of dye-sensitized titanium oxide solar cells is theoretically investigated herein. Different configurations in which a colloidal crystal can be implemented in such devices are modeled, and their absorptances compared. Experimental results on light-harvesting enhancement recently reported for periodically structured photoelectrodes are satisfactorily explained in terms of the appearance of multiple resonant modes localized in the absorbing layer when this is deposited onto one of the optical lattice surfaces. Longer matter-radiation interaction times for such frequencies result in higher absorption of those modes when compared to standard dye-sensitized solar cells. The effect of the finite size and the different characteristics of the photonic crystal on the optical absorption amplification effect is also discussed, new perspectives for colloidal-crystal-based photovoltaics being proposed.
RESUMO
In this paper, we describe a rapid, accurate, and convenient method for postsynthetically tuning the optical properties of colloidal photonic crystals. High quality photonic crystal films are first synthesized and then coated iteratively with layers of water-soluble polyelectrolytes. The coating process results in nanometer-scale shifts in the photonic stop band, a process which has been monitored by theoretical modeling. The results suggest a fundamentally different, reproducible layering mechanism inside the confined spaces of the colloidal crystal where polyelectrolyte multilayers are less densely packed.