A novel parallel configuration of dye-sensitized solar cells with double-sided anodic nanotube arrays
Energy & Environmental Science
In dye-sensitized solar cells based on anodic titania nanotube arrays, the low photocurrent in the backside-illuminated configuration has hindered their development. To increase the energy absorption and thus promote the photocurrent, a novel parallel configuration of dye-sensitized solar cells is proposed and achieved in this work on the basis of double-sided anodic nanotubes. The parallel connection is verified by electrochemical impedance spectroscopy measurements. The parallel cells exhibit
... an average 70% increment in photocurrent and 30% enhancement in efficiency as compared to the single cells, due to significantly increased surface area and highly reduced series resistance. Theoretical calculation and experimental fitting results demonstrate that a tube length of $30 mm is optimal for the nanotubes used in this study with backside-illuminated architecture. To reduce electron scattering and increase energy absorption, anodic titania nanotube arrays have been vigorously investigated in an attempt to substitute the conventional nanoparticle photoanodes used in dye-sensitized solar cells. However, the use of nanotubes is not as efficient as that of nanoparticles, for example, the highest efficiencies are $7% vs. $11%. One of the most important factors is the low dye loading amount for light harvesting in the nanotube photoanodes, which, in turn, gives rise to a low photocurrent as well as a low conversion efficiency. In this study, a novel parallel configuration of dye-sensitized solar cells is achieved based on doublesided anodic nanotubes. This structure doubles the dye loading amount and promotes the photocurrent in a unit solar cell. The parallel cells exhibit an average 70% increase in photocurrent and 30% increment in efficiency in contrast to the single cells, as a consequence of a highly increased surface area and considerably reduced series resistance.