Sensitization of ZnO by Light-Harvesting Antennas Composed of Multiple Stacked Dyes Grown by Liquid-Phase Molecular Layer Deposition

Abstract

We propose sensitization of ZnO by multi-dye stacked light-harvesting antennas grown by liquid-phase molecular layer deposition (LP-MLD), which grows organic tailored materials with designated molecular arrangements by sequentially exposing substrate surfaces to different kinds of source molecules in liquid phase. Using rose bengal (RB) and eosine (EO) for the p-type dyes, and crystal violet (CV) and brilliant green (BG) for the n-type dyes, three-dye stacked light-harvesting antennas were grown on ZnO. [ZnO/EO/CV/RB] structure exhibited a wide photocurrent spectrum, which is a superposition of the photocurrent spectra of EO, CV, and RB, rising up around 450 nm to extend over 600 nm in wavelength. In [ZnO/EO/BG/RB] structure the photocurrent generated by EO was drastically reduced. This can be attributed to the electron transfer from EO to BG, which is suggested by the energy-level schemes determined using the photoemission yield spectroscopy in air.