Sprayed aluminium -doped zincoxlide thin films for application as window material for solar cells
Njoroge, Walter Kamande
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Transparent and conducting ZnO films have been deposited by spray pyrolysis technique. The optimum conditions for deposition have been established. Optical and electrical properties have been investigated. Direct band gap of Zinc oxide films have been found to be 3.3 ev. Preparation of aluminium doped zinc oxide films is also presented. Effects of air and Vacuum annealing on the electrical and optical properties of doped and undoped zinc oxide films have been investigated. The changes in the electrical properties of ZnO films on annealing in air and vacuum are attributed to chemisorption and desorption of oxygen at the grain boundaries. The sheet resistance obtained was in the range 200-250 per square. An attempt was made to fabricate ZnO: AL/SiO2/p-Si solar cell which yielded an open circuit voltage of 0.22 V, short circuit current density of 1.4mA/cm2, fill factor of 0.25 and efficiency of 0.09% under 80 mW/cm2 insolation. The low efficiency can be attributed to high series resistance and thick interfacial oxide layer.