Visible to Near-Infrared Sensitization of Silicon Substrates via Energy Transfer from Proximal Nanocrystals: Further Insights for Hybrid Photovoltaics

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• 作者：Michael T. Nimmo ; Louis M. Caillard ; William De Benedetti ; Hue M. Nguyen ; Oliver Seitz ; Yuri N. Gartstein ; Yves J. Chabal ; Anton V. Malko
• 刊名：ACS Nano
• 出版年：2013
• 出版时间：April 23, 2013
• 年：2013
• 卷：7
• 期：4
• 页码：3236-3245
• 全文大小：828K
• 年卷期：v.7,no.4(April 23, 2013)
• ISSN：1936-086X

文摘

We provide a unified spectroscopic evidence of efficient energy transfer (ET) from optically excited colloidal nanocrystal quantum dots (NQDs) into Si substrates in a broad range of wavelengths: from visible (545 nm) to near-infrared (800 nm). Chemical grafting of nanocrystals on hydrogenated Si surfaces is achieved via amine-modified carboxy-alkyl chain linkers, thus ensuring complete surface passivation and accurate NQD positioning. Time-resolved photoluminescence (PL) has been measured for a set of CdSe/ZnS and CdSeTe/ZnS NQDs of various sizes and compositions grafted on Si and SiO₂ substrates. The measured acceleration of the PL decays on Si substrates is in good agreement with theoretical expectations based on the frequency-dependent dielectric properties of Si and NQD鈥揝i separation distances. A comparative analysis reveals separate contributions to ET coming from the nonradiative (NRET) and radiative (RET) channels: NRET is a dominant mechanism for proximal NQDs in the middle of the visible range and becomes comparable with RET toward near-infrared wavelengths. The broad range over which the ET efficiency is estimated to be at the level of 90% further supports the concept that hybrid nanocrystal/silicon thin-film photovoltaic devices could efficiently harvest solar energy across the entire spectrum of wavelengths.

Keywords:

hybrid nanostructures; solar cells; energy transfer; silicon substrates; semiconductor nanocrystals