Preperation And Properties Study Of Cds/(Pr,Gd,Dy, Y)/Cds Multilayer Films And Sb Doped ZnTe Thin Films

In this paper the research is based on the two key technologies (including the preparation of CdS window layer and ZnTe back contact layer) in preparation of high efficient CdTe solar cells. The main contents are as follows:1. Pure cadmium sulfide (CdS) thin films with the structure of CdS/CdS were prepared by using the chemical bath deposition (CBD). And with the different thickness of intercalated rare earth layer deposited by vacuum evaporation, CdS/Pr/CdS, CdS/Gd/CdS, CdS/Dy/CdS and CdS/Y/CdS multilayer films were prepared. The influence of different rare earth elements, rare earth layer thickness and heat treatment conditions on the membrane structure, surface morphology, chemical composition, optical and electrical properties of the films were studied, respectively. The results indicate that pure CdS/CdS films crystallize in the cubic structure and preferentially orient along (111) plane. It is an N type semiconductor and rich in Cd. The carrier concentration and resistivity of CdS/CdS films are about4.710×1014cm-3and7.286×103Ω·cm, respectively. For the CdS samples with intercalated rare earth layer, the deposition of Pr layer does not change the phase structure of CdS thin films but increases the intensity of cubic phase diffraction peak, and the conductive type of the film will be changed with the increase of Pr layer thickness. After the deposition of Gd (Y, Dy) layer between the two CdS layers, there appear a weak hexagonal phase structure and the conductivity of the film keeps N type. Compared with the CdS/CdS films, the resistivity of CdS/rare-earth/CdS samples reduces an order of magnitude, and the carrier concentration increases significantly. After the deposition of rare earth layer the uniformity and compactness of the films are improved and the composition has a trend to tend to the ideal ratio of chemical. At the same time, the optical transmission characteristics of CdS thin films in the visible range can be adjusted by depositing different thickness rare earth layer, and make its transmittance increase; but the effect on optical band gap is not obvious. For the present results, the optical and electrical properties of CdS/Gd/CdS multilayer films make it more suitable for the window layer materials of CdTe solar cells than that of the CdS/(Pr, Dy, Y)/CdS samples.2. ZnTe and Sb doped ZnTe poly crystalline thin films were prepared by vacuum evaporation on glass substrates and annealed in nitrogen environment. By using XRD, SEM, UV-VIS Spectrophotometer and Hall Effect Measurements, the crystal structure, surface morphology, optical and electrical properties of the films were examined, respectively. The effects of Sb-doping amounts and heat treatment on the performance of the films were studied. The results show that pure ZnTe film is a cubic structure and preferentially orients in the (111) plane and its conductive type is P type. Sb-doping does not change the crystal structure and conductive type of the films, but the intensity of diffraction peaks is lower than that of pure ZnTe films. The concentration of Sb directly affects the form of Sb in the ZnTe. Sb doping prevents the combination of Te and Zn, and leads to an increased concentration levels of Te in the ZnTe films. In addition, the optical transmittance and optical band gap of the films are determined by the concentration of Sb and annealing temperature. Sb-doping can also result in an obvious increasing of carrier concentration and reduce the resistivity, which significantly enhance the conductivity ability of the films.