Synthesis and wavelength-sensitive near-infrared photodetection performance of large-diameter single-walled carbon nanotubes with tailored bandgap distribution

单壁碳纳米管（SWCNTs）以不同的电子类型存在，其带隙可根据其结构进行调节。半导体（s-） SWCNTs还能够选择性地吸收近红外（NIR）范围内的光，从低于1微米一直到技术上重要的电信频段，最高可达几微米。因此，SWCNTs被认为是波长敏感的近红外光探测的理想材料，有望用于新一代光导体、光二极管和光晶体管。然而，基于SWCNTs的探测器的性能受到限制，主要是因为生长的SWCNTs通常包含金属纳米管和s-纳米管，而前者对于有效的光探测是非常不利的。因此，我们提出使用具有定制带隙分布的大直径s-SWCNTs制备波长敏感的近红外光电探测器，并研究所获得的器件的性能和工作机制。这项工作将是IMR团队和Darmstadt/Karlsruhe团队的联合研究工作，将引入他们在SWCNTs的受控合成和将SWCNTs集成到设备架构中的独特专业知识。我们将建立一种浮式催化剂化学气相沉积方法，通过催化剂设计和原位蚀刻相结合，实现高质量s-SWCNTs的连续可控合成。杂原子掺杂或液相色谱法将进一步优化带隙分布。我们将在s-SWCNTs薄膜或介质电泳溶液的基础上，使用具有定制带隙分布的大直径s-SWCNTs制作光电探测器，测量空间和光谱分辨的光电流响应，从而揭示光电流产生的机制。我们开发了一种器件架构，允许在目标波长范围内有效地将光转换为电流。我们将开发和优化基于swcnts的具有良好再现性和长期稳定性的近红外光电探测器。除了解决大直径半导体SWCNTs的受控合成和小带隙SWCNTs在近红外光谱中产生光电流的基本问题外，具有波长特异性吸收的近红外光电探测器的开发将是迈向无分散元件近红外光谱的重要一步。

Single-walled carbon nanotubes (SWCNTs) exist in different electronic types with tunable band gaps depending on their structure. Semiconducting (s-) SWCNTs are also able to selectively absorb light in the near-infrared (NIR) range from below one micron all the way through the technologically important telecom band up to several microns. In consequence, SWCNTs have been regarded as an ideal material for wavelength-sensitive NIR photodetection, which are expected to be used in new-generation photoconductors, optical diodes, and optical transistors. However, the performance of SWCNT-based detectors has been limited mainly due to the fact that as-grown SWCNTs usually contain both metallic and s- nanotubes, and the former is highly undesirable for efficient photodetection. Therefore, we propose to fabricate wavelength-sensitive NIR photodetectors using large-diameter s-SWCNTs with tailored band gap distributions and to study the performance and working mechanism of the devices obtained. This work will be a joint research effort of the IMR team and the Darmstadt/Karlsruhe team, bringing in their unique expertise in the controlled synthesis of SWCNTs and the integration of SWCNTs into device architectures. We will establish a floating catalyst chemical vapor deposition approach for the continuous, controllable synthesis of high-quality s-SWCNTs with tailored band gaps by combining catalyst design and in-situ etching. The band gap distribution will be further optimized by hetero-atom doping or liquid phase chromatography. We will fabricate photodetectors using large-diameter s-SWCNTs with tailored band gap distributions either on the basis of s-SWCNT films or from solution via dielectrophoresis, measure the spatially and spectrally resolved photocurrent response, and thereby reveal the mechanism of photocurrent generation. We develop a device architecture that allows efficient conversion of light into current for the targeted wavelength range will be developed and optimized SWCNT-based NIR photodetectors with good reproducibility and long term stability are targeted. Besides addressing fundamental questions related to the controlled synthesis of large-diameter, semiconducting SWCNTs and the photocurrent generation in the NIR from SWCNTs with small bandgap, the development of NIR photodetectors with wavelength-specific absorption will constitute an important step towards NIR spectrometry without dispersing elements.