Study of electronic defects in CdSe quantum dots and their involvement in quantum dot solar cells.

To enhance efficiencies of quantum dot CdSe/TiO(2) based solar cells, understanding of the space charge at the CdSe/TiO(2) interface is crucial. In this paper, the presence of a shallow acceptor in the CdSe quantum dots is found by means of a detailed impedance and Mott-Schottky (C(-2)-phi) study. Furthermore, it is clearly shown that this acceptor density decreases strongly with increasing quantum dot size. The presence of these defect states may give rise to Auger recombination in small quantum dots and therewith decrease the efficiency of quantum-dot-sensitized solar cells.