Localized Charges Control Exciton Energetics and Energy Dissipation in Doped Carbon Nanotubes
Localized Charges Control Exciton Energetics and Energy Dissipation in Doped Carbon Nanotubes
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DOI：
10.1021/acsnano.7b05543
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发表时间：
2017-10-01
期刊：
影响因子：
17.1
通讯作者：
Hertel, Tobias
中科院分区：
文献类型：
--
作者：
Eckstein, Klaus H.;Hartleb, Holger;Hertel, Tobias
通过化学或物理手段进行掺杂是未来半导体技术发展的关键。理想情况下，电荷载流子应该能够在均匀环境中自由移动。在这里，我们报告的证据表明，在电化学p型掺杂的半导体单壁碳纳米管（s-SWNT）的过剩载流子成为本地化，最有可能是由于不良屏蔽库仑相互作用与抗衡离子在亥姆霍兹层。第一激子吸收带的蓝移、加宽和不对称性的定量分析还揭示，掺杂导致s-SWNTs的硬分段，其中本征未掺杂的段被约4 nm宽的随机分布的电荷池分开。在这些掺杂段中的光吸收与空间上与中性激子分离的trions的形成相关联。在掺杂样品中的激子衰减的加速是由扩散激子运输，和非辐射衰减在电荷水坑内的3.2 ps的中度掺杂的s-SWNTs。结果表明，传统的带填充在s-SWNTs打破由于不均匀的电化学掺杂。
Doping by chemical or physical means is key for the development of future semiconductor technologies. Ideally, charge carriers should be able to move freely in a homogeneous environment. Here, we report on evidence suggesting that excess carriers in electrochemically p-doped semiconducting single-wall carbon nanotubes (s-SWNTs) become localized, most likely due to poorly screened Coulomb interactions with counterions in the Helmholtz layer. A quantitative analysis of blue-shift, broadening, and asymmetry of the first exciton absorption band also reveals that doping leads to hard segmentation of s-SWNTs with intrinsic undoped segments being separated by randomly distributed charge puddles approximately 4 nm in width. Light absorption in these doped segments is associated with the formation of trions, spatially separated from neutral excitons. Acceleration of exciton decay in doped samples is governed by diffusive excitors transport to, and nonradiative decay at charge puddles within 3.2 ps in moderately doped s-SWNTs. The results suggest that conventional band-filling in s-SWNTs breaks down due to inhomogeneous electrochemical doping.