Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nat Mater. 2010 Oct;9(10):833-9. doi: 10.1038/nmat2832. Epub 2010 Sep 12.
There has been renewed interest in solar concentrators and optical antennas for improvements in photovoltaic energy harvesting and new optoelectronic devices. In this work, we dielectrophoretically assemble single-walled carbon nanotubes (SWNTs) of homogeneous composition into aligned filaments that can exchange excitation energy, concentrating it to the centre of core-shell structures with radial gradients in the optical bandgap. We find an unusually sharp, reversible decay in photoemission that occurs as such filaments are cycled from ambient temperature to only 357 K, attributed to the strongly temperature-dependent second-order Auger process. Core-shell structures consisting of annular shells of mostly (6,5) SWNTs (E(g)=1.21 eV) and cores with bandgaps smaller than those of the shell (E(g)=1.17 eV (7,5)-0.98 eV (8,7)) demonstrate the concentration concept: broadband absorption in the ultraviolet-near-infrared wavelength regime provides quasi-singular photoemission at the (8,7) SWNTs. This approach demonstrates the potential of specifically designed collections of nanotubes to manipulate and concentrate excitons in unique ways.
人们对太阳能聚光器和光学天线重新产生了兴趣，以提高光伏能量收集和新型光电设备的性能。在这项工作中，我们通过电介质电泳将组成均匀的单壁碳纳米管 (SWNTs) 组装成排列整齐的长丝，这些长丝可以交换激发能量，将能量集中到具有径向光学能带隙梯度的核壳结构的中心。我们发现，当这种长丝从环境温度循环到仅 357 K 时，会发生异常尖锐、可逆的光发射衰减，这归因于强烈依赖温度的二级 Auger 过程。由主要为（6,5）SWNTs 的环形壳（E(g)=1.21 eV）和带隙小于壳的核（E(g)=1.17 eV（7,5）-0.98 eV（8,7））组成的核壳结构证明了这种浓缩概念：在紫外-近红外波长范围内的宽带吸收在（8,7）SWNTs 处提供准单峰光发射。这种方法展示了专门设计的纳米管集合在以独特方式操纵和浓缩激子方面的潜力。
