  Recently synthesized two-dimensional graphene-like material referred to as
graphenylene is a semiconductor with a narrow direct bandgap that holds great
promise for nanoelectronic applications. The significant bandgap increase can
be provided by the strain applied to graphenylene crystal lattice or by using
nanoribbons instead of extended layers. In this paper, we present the
systematic study of the electronic, optical and thermoelectric properties of
graphenylene nanoribbons using calculations based on the density functional
theory. Estimating the binding energies, we substantiate the stability of
nanoribbons with zigzag and armchair edges passivated by hydrogen atoms.
Electronic spectra indicate that all considered structures could be classified
as direct bandgap semiconductors. The absorption coefficient, optical
conductivity, and complex refractive index are calculated by means of the
first-principles methods and the Kubo-Greenwood formula. It has been shown that
graphenylene ribbons effectively absorb visible-range electromagnetic waves.
Due to this absorption, the conductivity is noticeably increased in this range.
The transport coefficients and thermoelectric figure of merit are calculated by
the nonequilibrium Green functions method. Summarizing the results, we discuss
the possible use of graphenylene films and nanoribbons in nanoelectronic
devices.
