الفهرس 
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Abstract
Amongst all different solar cell structures, the p-n heterojunction is one of the most promising technologies. Two different materials that match very well together to form such a p-n heterojunction, in particular those based on the ternary chalcopyrite CuInSez, has been discussed in this work. The characteristics of polycrystalline thin film CuInSep/CdS and CUI~S~~/C~~-so~lZar~ c,eSll s prepared by vacuum-evaporation techniques were described. In addition, a detailed description of CdS, Cdl-,Zn,S and CuInSe2 deposition procedures was given. The test setup of the solar cells established in the Optoelectronic Lab. in the Photovoltaic Centre of Newcastle Polytechnic, England, was also presented. Thin films of cadmium sulphide (CdS), were deposited using the thermal evaporation technique. Mixed-sulphide film (CdZnS) prepared by evaporation of CdS and ZnS powders from two separate sources was discussed. A novel technique which was used to produce the CuInSe* films was described. The deposition of a stack of elemental layers was found to produce large area, good quality CuInSe* films after processing in vacuum or under an inert gas ambient. Modification of selenide-film preparation in a rotating substrate vacuum-deposition apparatus was presented to achieve the consistency of reproducing the films which has led to the fabrication of high performance solar cells. Results presented in this thesis showed that the compound with the preferential chalcopyrite structure could be obtained after annealing at a temperature of more than 300oC. Film properties were dependent on annealing conditions and film composition. The final properties of the processed films were found to be very sensitive to the elemental layer thicknesses, Devices made by this technique using a thin film fabrication process were investigated. The results of the cellanalysis and cell-modelling studies on both the plain CdS and mixed Cdl-,ZnxS thin- film devices were presented. The measurements have been studied for four categories according to the resistivity values of CdS (or Cdl-,Zn,S) and CuInSe2 layers. from this study, it was evident that the response of the device was greatly dependent on the resistivity of both layers especially the CdS. Open-circuit voltage of 225 mV was obtained for this type of cell, while the short-circuit current was around 20 mA; AzO.7cm2. For the mixed sulphide film as a window layer, it has been found that the cells exhibited I,, comparable to cells with pure CdS, while the subsequent increase of Zn content in the sulphide layer exhibited higher open-circuit voltage (up to 270 mV) and poor fill factor. A slight increase of 213 mV in V,, was achieved by adding 16% Zn content, while had slight effect on FF. The heat treatment in oxygen environment was apparently necessary. I,, values has been improved from 3 mA to 20 mA after annealing periods up to 1 hr, but were rapidly degraded for longer duration. Solar cells fabricated by this technique have yielded efficiencies of 5.2% under 85% mWcm-2 illumination, with cell parameters: I,,=20 mA for an area 20.63 cm2, V,,t250 mV and FF:55%.- Solar device performance of this type could be improved by increasing CuInSe2 film thickness, using two layers of CuInSe2 and using antireflection coating. Conclusions drawn from this work indicate that the SEL technique for producing the CuInSe2 film was highly promising for the commercialisation of solar cells based on this material.