Electron transfer in a semiconductor heterostructure interface through electrophoretic deposition and a linker-assisted method

Abstract

Modulating the heterostructured interface of semiconductor nanocrystals is being widely explored to enhance the charge transfer rate in photoelectrochemical cells. Here we use electrophoretic deposition and a linker-assisted method to fabricate heterostructured photoanodes based on CdSe quantum dots (QDs) or CdSe(S) nanoplates (NPLs)/TiO₂ nanoparticles. The semiconductor nanocrystals exhibit red-shifted or dual photoluminescence emissions after electrophoretic deposition, due to the formation of surface traps. The calculated electron transfer rates in CdSe QDs/TiO₂ nanoparticle photoanodes fabricated via electrophoretic deposition and 3-mercaptopropionic acid (MPA)-assisted attachment are 5.5 × 10⁷ s⁻¹ and 2.7 × 10⁷ s⁻¹, respectively, which are both higher than those obtained from NPLs/TiO₂ nanoparticles ranging from 0.7 × 10⁷ s⁻¹ to 1.3 × 10⁷ s⁻¹. As a proof of concept, we used heterostructured semiconductor nanocrystals/TiO₂ nanoparticles as photoanodes for solar-driven hydrogen generation. Upon one sun illumination, the saturated photocurrent densities of photoanodes fabricated via electrophoretic deposition were found to be higher than those of photoanodes prepared via MPA-assisted attachment, while the corresponding photoanode shows inferior long-term photostability due to the formation of surface traps on the QDs or NPLs during the electrophoretic deposition process. These results provide useful information for engineering the surface/dimension/composition of semiconductor nanocrystals, their adsorption on porous TiO₂ films, and designing high-efficiency photoelectrodes in photoelectrochemical devices.