Quantum Dot-Dye Bilayer-Sensitized Solar Cells: Breaking the Limits Imposed by the Low Absorbance

ABSTRACT Here, we present a new DSSC design, consisting of sequential QDs and dye sensitization layers, that opens the path toward high optical density DSSCs that cover a significant part of the solar spectrum. Thenewconfiguration is enabled by the application of an amorphous TiO2 layer between the two sensitizers, allowing both electron injection from the outer absorber and fast hole extraction from the inner sensitizing layer. Utilizing two sensitizing layers, we obtain a 250% increase in cell efficiency compared to a QD monolayer cell. SECTION Energy Conversion and Storage C urrent conversion efficiency of dye-sensitized solarcells (DSSCs) reflects the limits imposed by the lowabsorbance of dye monolayers and the low efficiency of dye multilayers. The use of stronger absorbers such as quantum dots1-10 (QDs) has not led to an increase in effi-ciency due to the slow hole removal that enhances the recom-bination efficiency and instability of the nanocrystals when iodine-based electrolytes are used.11 In addition, the spectral properties of the relevant sensitizers require the use of mor