Assembly of CdSe onto mesoporous TiO2 films induced by a self-assembled monolayer for quantum dot-sensitized solar cell applications

A self-assembled monolayer (SAM) of 3-mercaptopropyl-trimethyoxysilane (MPTMS) is pre-assembled onto a mesoporous TiO2 film and is used as a surface-modified layer to induce the growth of CdSe QDs in the successive ionic layer adsorption and reaction (SILAR) process. Due to the specific interaction of the terminal thiol groups to CdSe, the MPTMS SAM is found to increase the nucleation and growth rates of CdSe in the SILAR process, leading to a well covering and higher uniform CdSe layer which has a superior ability, compared with the electrode without MPTMS, in inhibiting the charge recombination at the electrode/electrolyte interface. Furthermore, the performance of the CdSe-sensitized TiO2 electrode can further be improved by an additional heat annealing after film deposition, attributable to a better interfacial connection between CdSe and TiO2, as well as a better connection among CdSe QDs. The CdSe-sensitized solar cell prepared by the present strategy can achieve an energy conversion efficiency of 2.65% under the illumination of one sun (AM 1.5, 100 mW cm−2).