  Elementary semiconductors are rare and attractive, especially for
low-dimensional materials. Unfortunately, most of boron nanostructures were
found to be metallic, despite of their typical semiconducting bulk structure.
Herein, we propose a general recipe to realize low-dimensional semiconducting
boron. This unusual semiconducting behavior is attributed to charge transfer
and electron localization, induced by the symmetry breaking that divides boron
atoms into cations and anions. In addition, it is feasible to accomplish band
gap engineering by rationally designing various structures. Importantly, the
low-dimensional semiconducting boron are predicted to be an excellent
solar-cell material with the power conversion efficiency of higher than 20%,
paving the way for their promising optoelectronic applications.
