Novel conductive and flexible multi-walled polymeric nanotubes (MWPNTs) of poly(diazoaminobenzene) (PDAAB) were synthesized using diazoaminobenzene monomer for the first time in this report. The synthesis followed a one-pot, cost-effective, green and template-free procedure, in which aniline was used as initiator with 87% yield at room temperature. PDAAB was characterized with spectroscopic and microscopic methods such as Fourier-transform infrared (FTIR), UV–vis, X-ray diffractometry (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) as well as cyclic voltammetry (CV) and conductivity measurements. In addition, MWPNTs were used in the design of a novel single-layer polymer solar cell. PDAAB was sandwiched between TiO2 nanoparticle-modified fluorine-doped tin oxide (FTO) electrode and an aluminum electrode (FTO-TiO2│PDAAB│Al), as anode and cathode, respectively. Finally, various physical characteristics of the single-layer polymer solar cell were determined under simulated solar irradiation. Our proof-of-concept study demonstrated that MWPNTs provided a promising platform to develop polymer-based solar energy conversion and storage systems.