High performance photoelectrochemical hydrogen generation and solar cells with a double type II heterojunctionElectronic supplementary information (ESI) available: Electrochemical reaction in photoanodes and cathodes, the effects of MPA ligand exchange for QDSSCs, absorbance, transmittance and reflectance spectra, photoluminescence of samples with different sequences of CdSe and ZnS on TiO2, electrochemical impedance spectroscopy (EIS) measurements, equivalent circuit fitting results of EIS and

• Main Authors: Lai, Lai-Hung, Gomulya, Widianta, Protesescu, Loredana, Kovalenko, Maksym V, Loi, Maria A
• Format: Journal Article
• Language: English
• Published: 26.03.2014
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c4cp00632a

We report on the fabrication of CdSe quantum dot (QD) sensitized electrodes by direct adsorption of colloidal QDs on mesoporous TiO 2 followed by 3-mercaptopropionic acid (MPA) ligand exchange. High efficiency photoelectrochemical hydrogen generation is demonstrated by means of these electrodes. The deposition of ZnS on TiO 2 /CdSe further improves the external quantum efficiency from 63% to 85% at 440 nm under −0.5 V vs. SCE. Using the same photoelectrodes, solar cells with the internal quantum efficiency approaching 100% are fabricated. The ZnS deposition increases the photocurrent and chemical stability of the electrodes. Investigation of the carrier dynamics of the solar cells shows that ZnS enhances the exciton separation rate in CdSe nanocrystals, which we ascribe to the formation of a type II heterojunction between ZnS and CdSe QDs. This finding is confirmed by the dynamics of the CdSe photoluminescence, which in the presence of ZnS becomes noticeably faster. We report on the fabrication of CdSe quantum dot (QD) sensitized electrodes by direct adsorption of colloidal QDs on mesoporous TiO 2 followed by 3-mercaptopropionic acid (MPA) ligand exchange.