Peptide nanotubes (PNT), based on diphenylalanine (FF), have attracted considerable attention due to their biocompatibility, functional recognition, unique electronic properties, significant intrinsic polarization and strong piezoelectric effect. Each FF PNT has the total dipole moment oriented along the nanotube axis and significant polarization and piezoelectric constant reaching a large values. In addition, FF PNTs have photoelectronic properties, which are discussed in more detail in this article. Modeling and calculations of photoelectronic energy levels and band gap in FF PNT are carried out in this work by semi-empirical methods AM1, PM3 (HyperChem) and more developed methods PM7 (MOPAC) on the basis of previously developed our models of FF PNT structures, which correspond to experimental X-ray crystallographic data. The results obtained show that band gap Eg of the FF PNT is close to the threshold of the ultraviolet (UV) range (400–250 nm, or 3.1–4.96 eV) and can change under the influence of an electric field. This makes it possible to create, based on these FF PNTs, a solar-blind ultraviolet (SBUV) photodetector for detecting ozone holes in the UV. The finely tuned Eg parameters could be done using polymer ferroelectrics PVDF/P(VDF-TrFE), similarly as it was done for the infrared photodetectors based on dichalcogenides. The main FF PNTs photoelectronic features are presented and discussed in this paper.