Expansion of Range of Light-Producing Photocurrent by Using Mixed Dye in a Dye-sensitized Solar Cell

摘要

Dye sensitized solar cells have a relatively high conversion efficiency of about 10% and can be fabricated using an inexpensive wet method. If the conversion efficiency can be improved, it should be possible to produce a high-efficient solar cell at low cost. In the dye-sensitized solar cell, incident sunlight is absorbed by the dye on a porous TiO_2 film and produces electrons as carrier. Accdordingly, the range of the wavelength of light utilized as the energy source is narrower than that in semiconductor solar cells. In this study, we expanded the range of the light producing phogocurrent by using a mixture of Ru (bipy)_2 (SCN)_2 and Pheophorbide a dyes in dye-sensitized solar cell. The single-dye-sensitized solar cell with Ru (bipy)_2 (SCN)_2 has a high energy conversion efficiency of about 10%, and Pheophor-bide a was expected to enhance the photocurrent and not to obstruct the light absorption by Ru (bipy)_2 (SCN)_2. Howdver, the energy conversion efficiency of the mixed dye sensitized solar cell was samller than that of the single-dye-sensitized solar cell with Ru(bipy)_2(SCN)_2. Furthermore, we investigated the effect of the fabrication method of the counter electrode and of the mixing ratio of the dyes on the incident photon to current efficiency (IPCE) and on the evaluation parameters of solar cells such as open circuit voltage, short circuit current, fill factor and energy conversion efficiency.