The Studies Of The Preparation And Photoconductive Properties Of Organic/Inorganic Multilayer Films

In the thesis, the researches and development on the preparation, structure, photoconductive properties, and application of organic, inorganic and organic/inorganic heterojunction films were reviewed. Organic/inorganic multilayer films were prepared by vacuum sublimation and their structure and photoconductive properties were investigated. Copper-phthalocyanine (CuPc) was chose as the organic layer because it is a typical organic photoelectric semiconductor with high absorption coefficient and wide absorption spectrum in visible region. II-VI semiconductors were chose as the inorganic layers because they have high drift mobility. Accordingly, it is expected to get Organic/inorganic multilayer films that have excellent photoconductive properties. Furthermore, in order to investigate the mechanism of photoconductivity, Zinc sulphide (ZnS), which is transparent in visible region, and cadmium sulphide (CdS), which has optical absorption in visible region, were employed as inorganic layers. The CuPc, ZnS, CdS, CuPc/ZnS and CuPc/CdS multilayer films were prepared. The effects of the preparation parameters on the photoconductive properties of the multilayer films were analyzed. The optimal preparation parameters of the CuPc/ZnS and CuPc/CdS multilayer films were obtained. The photoconductive mechanisms of organic, inorganic and especial organic/inorganic multilayer films were discussed in the thesis.The effect of the substrate temperature on the structure and properties of CuPc film was studied firstly. With increasing the substrate temperature, the crystalline of CuPc film became better, the proportion of -CuPc increased, and the proportion of p-CuPc decreased in the CuPc films. The CuPc film had high absorption coefficient in visible region, while the drift mobility of CuPc film was too low, resulting in the low photosensitivity of CuPc films. The CuPc film got the optimal photosensitivity at the substrate temperature of 100C, the radio of the photocurrent to the dark current was 3.27.The prepared ZnS films had a cubic structure with a preferred orientation of (111) at different substrate temperatures. The ZnS films had high transmission in visible region. Up to the substrate temperature of 200 C, the optical band gap increased with increasing the substrate temperature, while at higher substrate temperatures, it decreased. The ZnS film at 200癈 had the biggest optical band gap of 3.579 eV. The resistivity anisotropy between in-plane and transverse direction was found in ZnS films. Up to the substrate temperature of 200 C, the in-plane resistivity of ZnS filmsdecreased with increasing the temperature. It increased with increasing the temperature at higher substrate temperatures. While the transverse resistivity of ZnS films followed inverse rule when the substrate temperature increased. The ZnS film at the substrate temperature of 200 C had the lowest in-plane resistivity, the highest transverse resistivity and in-plane drift mobility.The CdS films prepared at various substrate temperatures had a hexagonal structure with a preferred orientation of (002). With increasing the substrate temperature, the orientation growth became weak. At the low substrate temperatures, the optical band gap of CdS films increased with increasing the temperature. For high substrate temperatures, the optical band gap decreased with increasing the temperature. The optical band gap of CdS film at 150C reached the maximum, 2.459 eV. The in-plane resistivities of CdS films deposited at different substrate temperatures varied from 0.333 -cm to 18.924 -cm at room temperature. While the transverse resistivities were about 8 orders higher than the in-plane resistivities. Up to the substrate temperature of 150C, the in-plane resistivity of CdS films decreased with increasing the temperature. It increased with increasing the temperature at higher substrate temperatures. While the transverse resistivity of CdS films followed inverse rule when the substrate temperature increased. At the low substrate temperatures, the CdS films had high photosensi...