Performance Enhancement of Quantum-Dot-Sensitized Solar Cells by Potential-Induced Ionic Layer Adsorption and Reaction

Abstract

Successive ionic layer adsorption and reaction (SILAR) technique has been commonly adopted to fabricate quantum-dot-sensitized solar cells (QDSSCs) in the literature. However, pore blocking and poor distribution of quantum dots (QDs) in TiO₂ matrices were always encountered. Herein, we report an efficient method, termed as potential-induced ionic layer adsorption and reaction (PILAR), for in situ synthesizing and assembling CdSe QDs into mesoporous TiO₂ films. In the ion adsorption stage of this process, a negative bias was applied on the TiO₂ film to induce the adsorption of precursor ions. The experimental results show that this bias greatly enhanced the ion adsorption, accumulating a large amount of cadmium ions on the film surface for the following reaction with selenide precursors. Furthermore, this bias also drove cations deep into the bottom region of a TiO₂ film. These effects not only resulted in a higher deposited amount of CdSe, but also a more uniform distribution of the QDs along the TiO₂ film. By using the PILAR process, as well as the SILAR process to replenish the incorporated CdSe, an energy conversion efficiency of 4.30% can be achieved by the CdSe-sensitized solar cell. This performance is much higher than that of a cell prepared by the traditional SILAR process