Single-wall carbon nanotubes (SWCNTs) provide unique one-dimensional (1D) platforms for exploring nonintuitive many-body physics unique to 1D systems as well as for developing quantum devices for computation, sensing, and communication. There are semiconducting and metallic SWCNTs, and semiconducting SWCNTs, being direct-gapped, are promising for building revolutionary optoelectronic devices such as ultralow-threshold lasers and ultrahigh-efficiency solar cells. During the last decade, individual semiconducting SWCNTs have been extensively studied. However, optical properties of macroscopic assemblies and devices of SWCNTs have yet to be explored. In this work, we studied electroluminescence devices based on chirality-purified (6,5) SWCNT films, demonstrating intense near-infrared light emission with high efficiencies through the process of impact ionization. By eliminating residual carriers through annealing, we were able to achieve a more than 100% increase in efficiency for light emission per carrier. In addition, in films in which SWCNTs are well aligned, we made an unusual observation that the polarization of emitted photons depends on the direction of the current with respect to the SWCNT alignment direction. These results are not only fascinating but also important for developing unique macroscopically 1D optoelectronic devices based on aligned SCWNT films.