Size‐Quantized Nanocrystalline Semiconductor Films
Size‐Quantized Nanocrystalline Semiconductor Films
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尺寸量子化纳米晶半导体薄膜
DOI：
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发表时间：
1993
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通讯作者：
G. Hodes
中科院分区：
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作者：
G. Hodes
本文回顾了我们在纳米晶半导体薄膜方面的工作，纳米晶半导体薄膜在三个维度上表现出明显的尺寸量子化效应，表现为光学吸收光谱中的大蓝移。这些薄膜是通过化学溶液沉积（CdSe 和 PbSe）或通过非水电解质电沉积（CdSe 和 CdS）制备的。除了 PbSe 的纳米晶体被基质包围外，薄膜均由聚集的纳米晶体组成。晶体尺寸（通常为 6 nm）以及吸收光谱可以通过沉积温度、沉积过程中的照明（对于化学沉积薄膜）、溶液成分和后退火来控制。讨论了化学沉积薄膜的晶体尺寸对实验参数（温度、光照、反应物浓度）的依赖性。 CdSe 纳米晶体外延电沉积在单晶 Au 上。纳米晶体的分布（分离的或聚集的）可以通过沉积电流和温度来控制。所有这些薄膜都表现出光电化学行为，但没有相应的固态光伏行为。提出了一种基于电子/空穴分离的模型，该模型是通过电荷注入电解质中的动力学差异而不是通过半导体中的内置空间电荷层来实现的。通过半导体表面特性和/或电解质的变化，相对于光电流流动方向，薄膜可以表现为“n”型或“p”型，与该模型一致。
This paper is a review of our work on nanocrystalline semiconductor films which exhibit pronounced size quantization effects in three dimensions, manifested by large blue-shifts in their optical absorption spectra. The films are prepared by either chemical solution deposition (CdSe and PbSe) or by electrodeposition from nonaqueous electrolytes (CdSe and CdS). Except for PbSe, where the nanocrystals are surrounded by a matrix, the films are comprised of aggregated nanocrystals. Crystal size (typically from 6 nm), and therefore absorption spectra, can be controlled by deposition temperature, illumination during deposition (for chemically deposited films), solution composition, and post annealing. The crystal size dependence of chemically-deposited films on experimental parameters (temperature, illumination, reactant concentrations) is discussed. CdSe nanocrystals were epitaxially electrodeposited on single-crystal Au. The nanocrystal distribution (isolated or aggregated) could be controlled by deposition current and temperature. All these films exhibit photoelectrochemical behavior but no corresponding solid state photovoltaic behavior. A model is proposed based on electron/hole separation by kinetic differences in charge injection into an electrolyte rather than by a built-in space charge layer in the semiconductor. The films can behave as both ‘n’ - or ‘p’-type, with respect to direction of photocurrent flow, by changes in the semiconductor surface properties and/or the electrolyte, in agreement with this model.