High efficiency of dye-sensitized solar cells with two-layer mesoporous photoanodes fabricated in a low temperature process

We fabricated, for the first time, the dye-sensitized solar cells (DSSCs) with two-layer mesoporous photoanodes in a low-temperature process, revealing a significant improvement on the performance. The lower one of the two mesoporous layers was prepared from highly crystalline, reactive anatase TiO2 (h-TAc), which was synthesized by the hydrothermal method. Without any post treatment on the photoanodes, the power conversion efficiency (PCE) of the DSSCs incorporating h-TAc can reach as high as 6.65%, further exceeding most of the improvement without post treatment in the low temperature process reported in the literature. The enhanced PCE may be attributed to the increase of dye adsorption and the decrease of charge transfer resistance. We found the decrease of the charge interface resistance resulted from the strong chemical bonding among h-TAc particles, catalyzed by the carboxyl groups on the h-TAc surface.