  The optoelectronic properties of single- and double-wall carbon nanotubes
(CNTs) noncovalently functionalized with tetraphenylporphyrins (TPPs) are
addressed by dispersion-corrected ab initio calculations. Five CNT species with
different chiralities were considered. We find that the most stable
configurations are those where the CNTs are fully covered by TPPs, exhibiting
binding energy of about 2~eV/TPP. The semiconducting CNT-TPP compounds show
optical response characterized by a strong absorption associated to the TPP
bands, with increasing intensity with the TPP concentration. In addition,
molecular dynamic simulations show that the compounds would be stable at
temperatures as high as 100$^{\circ}$C.
