Interplay Between Structure, Stoichiometry, and Electron Transfer Dynamics in SILAR-based Quantum Dot-Sensitized Oxides

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• 作者：Hai Wang ; Irene Barcel贸 ; Teresa Lana-Villarreal ; Roberto G贸mez ; Mischa Bonn ; Enrique C谩novas
• 刊名：Nano Letters
• 出版年：2014
• 出版时间：October 8, 2014
• 年：2014
• 卷：14
• 期：10
• 页码：5780-5786
• 全文大小：409K
• ISSN：1530-6992

文摘

We quantify the rate and efficiency of picosecond electron transfer (ET) from PbS nanocrystals, grown by successive ionic layer adsorption and reaction (SILAR), into a mesoporous SnO₂ support. Successive SILAR deposition steps allow for stoichiometry- and size-variation of the QDs, characterized using transmission electron microscopy. Whereas for sulfur-rich (p-type) QD surfaces substantial electron trapping at the QD surface occurs, for lead-rich (n-type) QD surfaces, the QD trapping channel is suppressed and the ET efficiency is boosted. The ET efficiency increase achieved by lead-rich QD surfaces is found to be QD-size dependent, increasing linearly with QD surface area. On the other hand, ET rates are found to be independent of both QD size and surface stoichiometry, suggesting that the donor鈥揳cceptor energetics (constituting the driving force for ET) are fixed due to Fermi level pinning at the QD/oxide interface. Implications of our results for QD-sensitized solar cell design are discussed.

Keywords:

Quantum dot stoichiometry; SILAR; PbS quantum dots; epitaxial growth; electron transfer; THz spectroscopy; quantum dot-sensitized solar cells