  We present ionization structures of IC 2003, a planetary nebula with [WR]
central star, using a 1-D dusty photo-ionization code: "CLOUDY 17.03". The
photo-ionization model is constrained by archival UV emission line fluxes,
medium-resolution optical spectroscopy, $IRAS$ $25 \mu m$ flux, absolute
$H\beta$ flux, and the mean angular size of the nearly spherical optical
nebula. To constrain the carbon abundance and the effect of photo-electric
heating in the ionized gas, we used UV emission lines. We considered an
amorphous carbon dust grain with MRN and KMH size distributions to address the
importance of photo-electric heating in the ionized nebula. We show that KMH
grain size distribution with quantum dust heating reproduces the observations
quite well. We construct the ionization structures of different elements at
their different ionization stages in the nebula. We derive the physical
properties of the planetary nebula and its chemical composition, as well as the
parameters of its central star. The estimated nebular dust-to-gas mass ratio is
$2.37\times 10^{-3}$, and the enhanced photo-electric heating yielded by small
dust grains is $9.4\%$ of the total heating. We considered the H-poor model
atmosphere for the central star; the effective temperature of the central star
is 177kK, the specific gravity log(g) is 6, and its luminosity ($L_*$) is 6425
$L_\odot$. The derived central star parameters plotted on stellar evolutionary
tracks correspond to a central star mass of 0.636$M_\odot $ and to a progenitor
mass of 3.26$M_\odot$.
