Sensitization of p-GaP with CdSe quantum dots: light-stimulated hole injection.

The sensitization of p-GaP by adsorbed CdSe quantum dots has been observed. Nondegenerately doped, planar p-GaP(100) photoelectrodes consistently showed sub-band-gap (>550 nm) photoresponsivity in an aqueous electrolyte containing Eu(3+/2+) when CdSe quantum dots (diameters ranging from 3.1 to 4.5 nm) were purposely adsorbed on the surface. Both time-resolved photoluminescence decays and steady-state photoelectrochemical responses supported sensitized hole injection from the CdSe quantum dots into p-GaP. The observation of hole injection in this system stands in contrast to sensitized electron injection seen in other metal oxide/quantum dot material combinations and therefore widens the possible designs for photoelectrochemical energy conversion systems that utilize quantum dots as light-harvesting components.