Recent Advances of Dye-Sensitized Solar Cells and Integrated Modules at SHARP

Abstract

An equivalent circuit for DSCs was studied using electrochemical impedance spectroscopy measurement, and the improvements of conversion efficiency of DSCs for not only single cells but also integrated modules were investigated. Further improvement of cell characteristics of DSCs was also investigated from the view point of modified TiO₂ films and series-internal resistance design. The series-internal resistance elements were found to correlate positively with the sheet resistance of the transparent conducting oxide and the thickness of the electrolyte layer and negatively with the roughness factor of the platinum counter-electrode. The short circuit current density (Jsc) of the DSCs was effectively improved by use of a high-haze TiO₂ film. In addition, the analysis of TiO₂/dye interface by scanning probe microscopy and transient absorption spectroscopy were also useful for the study. As a result, the maximum single cell conversion efficiency of over 11% was obtained. Furthermore, an integrated DSC module composed of many rectangular cells connected in series was fabricated and the efficiency was increased to 8.4% (confirmed by AIST) by realizing high active area and high uniformity.