Fabrication of Advanced Thin Film Photovoltaic Materials using Ternary Compounds as Evaporation Materials and Trial Production of their Solar Cells

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In this research, chalcopyrite Cu(In,Ga)(S,Se)_2 thin films were prepared by the new process applicable to the large scale production, which was the sequential evaporation from ternary compounds. Moreover, their solar cells were manufactured by way of trial and their properties were investigated.(1)The new process to prepare Cu(In,Ga)Se_2 thin films was examined. In the first step, Cu-In-Ga-Se layer was evaporated from CuInSe_2 and CuGaSe_2 ternary compounds onto the Mo/soda-lime glass substrate. In the second step, In-Se layer was deposited from In_2Se_3 compound at a substrate temperature of 490℃. Finally, only Se was effused at the same substrate temperature. The surface composition of Cu(In,Ga)Se_2 thin film could be controlled in the optimum range by adjusting the amount of In_2Se_3.(2)Cu(In,Ga)(S,Se)_2 thin films were prepared by simultaneously evaporating In_2Se_3 and In_2S_3 compounds in the second step of the above process. The S content in Cu(In,Ga)(S,Se)_2 thin films was inc … More reased with increasing the amount of In_2S_3 in the second step.(3)Cu(In,Ga)(S,Se)_2 thin films were prepared by thermal crystallization from CuInGaSe/CuGaSe stacked precursor in S and Se atmosphere. The precursors were prepared by evaporating consecutively from the CuGaSe_2 and Cu(In,Ga)Se_2 compounds. The grain sizes in Cu(In,Ga)(S,Se)_2 thin films were increased with increasing the crystallization temperature.(4)The best solar cell using Cu(In,Ga)Se_2 thin film prepared by the new process demonstrated Voc=330mV, Isc=28.3mA/cm^2, FF=0.461 and Eff=4.31% without AR-coating. The open circuit voltage in Cu(In,Ga)(S,Se)_2 thin film solar cell was improved by using In_2S_3 compound as a S source.As a result, the method to produce Cu(In,Ga)(S,Se)_2 thin films from ternary compounds was clarified for application to fabricate an advanced thin film solar cell with low cost and high efficiency. Moreover, the trial production of their solar cells suggested the future direction of research for improvement in solar cell performance. Less