  By means of a multi-scale first-principles approach, a description of the
local electronic structure of two-dimensional and narrow phosphorene sheets
with various types of modifications is presented. First, a rational argument
based on the geometry of the pristine and modified P network, and supported by
the Wannier functions formalism is introduced to describe a hybridization model
of the P atomic orbitals. {\it Ab initio} calculations show that
non-isoelectronic foreign atoms form quasi-bound states at varying energy
levels and create different polarization states depending on the number of
valence electrons between P and the doping atom. The quantum transport
properties of modified phosphorene ribbons are further described with great
accuracy. The distortions on the electronic bands induced by the external
species lead to strong backscattering effects on the propagating charge
carriers. Depending on the energy of the charge-carrier and the type of doping,
the conduction may range from the diffusive to the localized regime.
Interstitial defects at vacant sites lead to homogeneous transport fingerprints
across different types of doping atoms. We suggest that the relatively low
values of charge mobility reported in experimental measurements may have their
origin in the presence of defects.
