Tetrapod CdSe-sensitized macroporous inverse opal electrodes for photo-electrochemical applications

Abstract

Quantum dots (QDs) possess promising characteristics that are important to light harvesting, but their mesoscale size limits their application in the direct sensitization of TiO₂ porous films for photo-electrochemical cells (PECs). Here, inverse opal (IO) TiO₂ structures were sensitized by tetrapod-CdSe (tp-CdSe) QDs, which were used in visible-light PECs. Because of the interconnected macropores in the IO structure, tp-CdSe penetrated the entire film and deposited on its surface. In contrast, infiltration was limited to the surface of the conventional mesoporous TiO₂ film. The amount of tp-CdSe deposited was dependent on the immersion time of the film in the tp-CdSe dispersion. Optimum deposition of tp-CdSe was observed at the highest photocurrent density. Light harvesting, thus the photocurrent, increased with increasing amounts of deposit, but there was a corresponding decrease in electron lifetime. The maximum photocurrent density per Cd mass was 0.474 mA cm⁻², which is greater than previous results from experiments using QD-sensitized PECs. We thus believe that a combination of tetrapod QDs and the TiO₂ IO film may provide a new platform for PEC electrodes.