Preparation Of Cadmium Sulphide Thin Film And Its Application On Copper Indium Gallium Diselenide Thin Film Solar Cells

CIGS(CuIn_1-xGa_xSe) thin film solar cell has been intensively researched due to its high conversion efficiency and potentially low manufacture cost. N-type semiconductor thin film is deposited on p-type CIGS absorber layer to form p-n junction to separate light-excited carriers. Chemical bath deposition(CBD) is a low cost growth technique capable of producing good quality semiconductor thin film over large area at low temperature. Therefore, it is widely used in laboratories and PV industry to make CIGS solar cells.The CdS films were deposited on glass and CIGS substrates from a chemical bath containing cadmium iodide, thiourea and ammonium hydroxide in this thesis. Different volumes were added into reaction bath to change the concentration of reagents. SEM images,XRD patterns and optical transmission data were measured to analyze the effects of deposition parameters on the qualities of CdS films. CdS films were annealed in air at different temperatures. Results showed that qualities of CdS films were related to deposition parameters and annealing temperatures. The reaction solution was creatively optimized according to the conversion efficiencies of CIGS solar cells. The best cell at present yielded an active area efficiency of 14.8%.A large quantity of waste solution is produced during the process of CBD-CdS films. It severely endangers the environment if treated improperly. This thesis innovatively carried on relatively systematic experiments to reuse waste solution. The CdS films were deposited on glass and CIGS substrates from a chemical bath containing cadmium iodide, thiourea and ammonium hydroxide using filtered waste solution as solvent. Experiment results showed that it was completely possible to use waste solution to make CIGS solar cells comparable to those made using purified water as solvent.