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The extraordinary one-dimensional properties of carbon nanotubes have captivated scientists and engineers since their discovery in the early 1990s. In particular, semiconducting single-wall carbon nanotubes (SWCNTs) are highly promising for optoelectronic applications because of their diameter-dependent direct band gaps and strong, tunable light–matter interactions. However, the prevalence of structural disorder, misalignment, and chirality heterogeneity in macroscopic assemblies has hindered their practical applications. Recently, advanced assembly methods, combined with post-growth chirality separation techniques, have enabled the fabrication of wafer-scale, nearly crystalline films of highly aligned and densely packed SWCNTs with tailored properties. In this Opinion, we discuss how these films provide a transformative platform for engineering “Single 3 ” heterostructures—assemblies that are simultaneously single -crystal, single -chirality, and single -wall. Stacking these layers with nanometer-scale precision and tunable thicknesses allows for the realization of artificial bilayer junctions, quantum wells, and superlattices. We posit that these architectures will enable a new generation of high-performance devices, including lasers, photodiodes, solar cells, and single-photon emitters.
Chang et al. (Wed,) studied this question.