vacuum sublimation method was used to purify the homegrown 3,4,9,10 perylenetetracarboxylic dianhydride（PTCDA）powder with a purity of 98% in its sublimation point of 450 ℃. With Bill’s law and ultraviolet-visible spectrophotometer testing analysis, its purity reached to 99.8%. Meanwhile, the contents of C and H elements in the pre-and post-purified molecules were also measured by using elemental analyzer. The measured results indicate that the contents of C and H elements in the post-purified the molecules are very close to the theoretical value. H element in the molecular structure was investigated with nuclear magnetic resonance (NMR) spectroscopy and the results demonstrated that there are an equal number of H atoms in two different chemical environments and it can only be located on the aromatic ring. By discussing the chemical bond formation of PTCDA molecules, the C, H and O atoms in high purity PTCDA molecules are mainly covalent bonds. The crystalline state and crystal structure of this organic material were tested and analyzed by X-ray diffractometer. The results suggest that the post-purified PTCDA power existed α-PTCDA and β-PTCDA two phases, in which α-PTCDA phase is major component while β-PTCDA phase accounts for about one five of the total ingredients. Besides, the crystal cell belonged to bottom-centered monoclinal structure. Meanwhile, the crystal state, grain size and band structure of PTCDA single crystal thin films formed on the surface of p-type silicon in its sublimation point are investigated in detail. During the high-purity α-PTCDA forming organic single thin film on the surface of p-type single silicon, the π-electron cloud covered on the top, bottom and two sides of its thin film’s molecular layer plane. Due to the formation of delocalized bond that attributed to the overlap of the outermost valence electron orbital of C, H, O atom, the valence electrons generate co-movement and the energy level splitting for the band. The energy difference between valence band and the first tight binding is 2.2 eV which lead to this organic material possessing the properties of semiconductor conduction. In addition, this organic material with the intrinsic carrier concentration for 1014 cm-3 belong to weak p-type organic semiconductor material. This organic material combines with the surface of p-type silicon to form hetehomo-type heterojunction which is provided with excellent response for visible light to near infrared wavelengths of light.