Efficient sensitization of ZnO nanoporous films with CdSe QDs grown by Successive Ionic Layer Adsorption and Reaction (SILAR)

Quantum Dot Sensitized Solar Cells are emerging as a new type of photovoltaic device. In this context, ZnO nanoporous films have been sensitized to the visible by depositing CdSe quantum dots (QDs) by the so-called Successive Ionic Layer Adsorption and Reaction (SILAR) method. Experiments using a ZnO(0 0 0 1) single crystal reveal that the surface is nearly fully covered with CdSe QDs even after only 2 SILAR cycles. In agreement, Transmission Electron Microscopy images of the nanoporous electrodes show the initial generation of small nanoparticles, which finally leads to the formation of large aggregates. In the absence of an electron scavenger in solution, the CdSe-sensitized ZnO electrodes show an Incident Photon to Current Efficiency as high as 70%, similar to previously reported values for TiO2 electrodes. In addition, zinc oxide photoanodes prepared by SILAR are also more efficient than those sensitized with colloidal CdSe QDs attached to the oxide through molecular linkers. The prospects of preparing complete quantum dot solar cells based on ZnO as electron conducting phase are briefly discussed.