Trap states and carrier dynamics of TiO2 studied by photoluminescence spectroscopy under weak excitation condition
Trap states and carrier dynamics of TiO2 studied by photoluminescence spectroscopy under weak excitation condition
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DOI：
10.1039/b925277k
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发表时间：
2010-01-01
影响因子：
3.3
通讯作者：
Li, Can
中科院分区：
文献类型：
--
作者：
Wang, Xiuli;Feng, Zhaochi;Li, Can
在弱激发条件下，利用光致发光技术研究了锐钛矿型和金红石型 TiO2，其中陷阱态在载流子动力学中起着至关重要的作用。锐钛矿的可见光发射和金红石的近红外 (NIR) 发射均表现出长达毫秒的极长寿命。衰变过程可以通过对应于捕获-去捕获效应的幂律衰变来很好地描述。这些结果表明锐钛矿型和金红石型 TiO2 的发光过程与陷阱态有密切的关系。可见发射带被分配给供体-受体重组。氧空位和羟基分别主要充当供体和受体位点。近红外发光源自捕获电子与自由空穴的复合，而捕获电子通过直接捕获或陷阱到陷阱跳跃两种路径形成。锐钛矿型和金红石型 TiO2 中的陷阱态可能在很大程度上影响 TiO2 的光催化过程并决定固定光照下的光催化活性。
Anatase and rutile TiO2 were investigated with photoluminescence techniques under the weak excitation condition, where trap states play a vital role in carrier dynamics. The visible emission of anatase and near-infrared (NIR) emission of rutile both exhibit extremely long lifetimes up to milliseconds. The decay processes can be well described by the power-law decay which corresponds to the trapping-detrapping effect. These results indicate that the luminescence processes in both anatase and rutile TiO2 have a close relationship with trap states. The visible emission band was assigned to the donor-acceptor recombination. Oxygen vacancies and hydroxyl groups mainly serve as the donor and acceptor sites, respectively. The NIR luminescence is originated from the recombination of trapped electrons with free holes, while the trapped electrons were formed through two paths, direct trapping or trap-to-trap hopping. The trap states in anatase and rutile TiO2 may largely influence the photocatalysis process of TiO2 and determine the photocatalytic activity under stationary illumination.