Atomically thin nanowires (NWs) can be synthesized inside single-walled carbon nanotubes (SWCNTs) and feature unique crystal structures. Here we show that HgTe nanowires formed inside small-diameter (<1 nm) SWCNTs can advantageously alter the optical and electronic properties of the SWCNTs. Metallic purification of the filled SWCNTs was achieved by a gel column chromatography method, leading to an efficient extraction of the semiconducting and metallic portions with known chiralities. Electron microscopic imaging revealed that zigzag HgTe chains were the dominant NW geometry in both the semiconducting and metallic species. Equilibrium-state and ultrafast spectroscopy demonstrated that the coupled electron–phonon system was modified by the encapsulated HgTe NWs, in a way that varied with the chirality. For semiconducting SWCNTs with HgTe NWs, Auger relaxation processes were suppressed, leading to enhanced photoluminescence emission. In contrast, HgTe NWs enhanced the Auger relaxation rate of metallic SWCNTs and created faster phonon relaxation, providing experimental evidence that encapsulated atomic chains can suppress hot carrier effects and therefore boost electronic transport.

Bringing together the expertise from fifteen laboratories the current-voltage characteristics of a solar cell are modeled using contactless terahertz and microwave measurements. To this end, the impact of measurement conditions, alternate interpretations, and experimental inter-laboratory variations are discussed. For a neat (Cs,FA,MA)Pb(I,Br)3 thin film, the implied resistance-free JV-curve and the fill factor losses by its finite mobility are revealed.

Terahertz (THz) spectroscopy is an ideal non-contact and non-destructive technique that probes the electrical conductivity of nanomaterials. This review presents the current status of research in the THz properties of quasi-1D materials, such as nanotubes (NTs) and NT heterostructures. The detailed description of THz experimental methods (THz time-domain spectroscopy, optical pump-THz probe spectroscopy) and conductivity extraction methods are presented along with the physical models (Drude, plasmon, effective medium theories, etc.) supporting them. Optoelectronic applications, such as optical modulators, switches, and shielding devices, are discussed and illustrate a bright future for these materials.

Full control of the ellipticity of broadband pulses of THz radiation, from linear to left- or right-handed circular polarization, was demonstrated via a four-pixel photoconductive emitter with an integrated achromatic waveplate. Excellent polarization purity and accuracy were achieved, with Stokes parameters exceeding 97% for linear and circular polarization, via a robust scheme that corrected electrically for polarization changes caused by imperfect optical elements. Furthermore, to assess the speed and precision of measurements of the THz polarization, we introduced a figure of merit, the standard error after one second of measurement, found to be 0.047° for the polarization angle.