Details

Autor(en) / Beteiligte

• Zhu, Haiming
• Song, Nianhui
• Lian, Tianquan

Titel

Controlling Charge Separation and Recombination Rates in CdSe/ZnS Type I Core−Shell Quantum Dots by Shell Thicknesses

Ist Teil von

• Journal of the American Chemical Society, 2010-10, Vol.132 (42), p.15038-15045

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2010

Quelle

MEDLINE

Beschreibungen/Notizen

• Type I core/shell quantum dots (QDs) have been shown to improve the stability and conversion efficiency of QD-sensitized solar cells compared to core only QDs. To understand how the shell thickness affects the solar cell performance, its effects on interfacial charge separation and recombination kinetics are investigated. These kinetics are measured in CdSe/ZnS type I core/shell QDs adsorbed with anthroquinone molecules (as electron acceptor) by time-resolved transient absorption spectroscopy. We show that the charge separation and recombination rates decrease exponentially with the shell thickness (d), k(d) = k 0 e −βd , with exponential decay factors β of 0.35 ± 0.03 per Å and 0.91 ± 0.14 per Å, respectively. Model calculations show that these trends can be attributed to the exponential decrease of the 1S electron and hole densities at the QD surface with the shell thickness. The much steeper decrease in charge recombination rate results from a larger hole effective mass (than electron) in the ZnS shell. This finding suggests possible ways of optimizing the charge separation yield and lifetime by controlling the thickness and nature of the shell materials.