Gross Dieter, Susha Andrei S, Klar Thomas A, Da Como Enrico, Rogach Andrey L, Feldmann Jochen
Photonics and Optoelectronics Group, Physics Department and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, 80799 Munich, Germany.
Nano Lett. 2008 May;8(5):1482-5. doi: 10.1021/nl080489a. Epub 2008 Apr 15.
We report on charge separation between type II aligned CdTe and CdSe nanocrystals. Two types of electrostatically bound nanocrystal structures have been studied: first, clusters of nanocrystals hold together by Ca(II) ions in aqueous solution and, second, thin film structures of nanocrystals created with layer-by-layer deposition in combination with polyelectrolytes. In both types of structures, short interparticle distances of less than 1 nm have been achieved, whereby the isolating organic ligands on the nanocrystal surfaces and/or the polymer monolayers act as tunneling barriers between nanocrystals. We have observed an efficient quenching of photoluminescence and a reduced emission lifetime for CdTe nanocrystals in both types of type II heterostructures. This result is explained by a spatial charge separation of the photoexcited electron-hole pairs due to tunneling of charge carriers through the thin organic layer between CdTe and CdSe nanocrystals. Type II heterostructures demonstrated here may find future applications in photovoltaics.
我们报道了II型排列的碲化镉（CdTe）和硒化镉（CdSe）纳米晶体之间的电荷分离。我们研究了两种类型的静电结合纳米晶体结构：第一，在水溶液中通过钙离子（Ca(II)）结合在一起的纳米晶体簇；第二，通过与聚电解质逐层沉积形成的纳米晶体薄膜结构。在这两种结构中，都实现了小于1纳米的短粒子间距离，其中纳米晶体表面的隔离有机配体和/或聚合物单分子层充当纳米晶体之间的隧穿势垒。我们在两种类型的II型异质结构中都观察到碲化镉纳米晶体的光致发光有效猝灭和发射寿命缩短。这一结果可以通过光激发的电子-空穴对由于电荷载流子隧穿穿过碲化镉和硒化镉纳米晶体之间的薄有机层而发生的空间电荷分离来解释。本文展示的II型异质结构可能在未来的光伏领域找到应用。
