CdS quantum dots grown by in situ chemical bath deposition for quantum dot-sensitized solar cells

CdS quantum dots (QDs) are grown on mesoporous TiO₂ films by 3 to 13 repeated cycles of in situ chemical bath deposition (CBD). The overall energy conversion efficiency of CdS quantum dot-sensitized solar cells (QD-SSCs) increases as the number of cycles increases to the eight - peaking at 2.13. This is attributable to efficient light harvesting and charge-collection resulting from enhanced light absorption and faster charge transport. However a further increase of CBD cycles to thirteen reduces QD-SSCs performance, despite better light absorption in the long wavelengths. This is attributed to decreased charge-injection efficiency, which is due to reduced driving forces of carrier injection, increased trap-mediated recombination in the QDs, and hindered ion transport.