Study on the Molecular Beam Deposition of CuInSe2 Thin Film

• Main Authors: Jun-Xian Hung, 黃俊憲
• Other Authors: Herng-Yih Ueng
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/07051813663172868817

碩士 === 國立中山大學 === 電機工程學系研究所 === 91 === The objective of this proposed study is to develop the new material CuInSe2 for large area, low cost and high efficiency commercial CuInSe2 based solar cell for the solar resource in Taiwan. The compositions of CuInSe2 films are modulated precisely to obtain an ideal electrical and optical characteristics resulting in high conversion efficiency for commercial solar cell applications. Numerous experimental investigations have shown the electrical properties of undoped CuInSe2 are dominated by various types of electrically active intrinsic defects caused by the deviations from the ideal stoichiometry. Without any intentional doping CuInSe2 can be made n-type and p-type conducting with carrier concentrations varying over many orders of magnitude either by slightly changing the composition of the material during growth or by appropriate post-growth annealing procedures. Several attempts have been made successfully by the crucial construction and application of intrinsic defect chemistry model to investigate the trend in the conductivity of CuInSe2, however, there investigation still remain no clear evidence to directly correlate composition and electrical properties reported by several authors, and the results of experimental data shows in contradiction to the intrinsic defect model. According to the point defect model, that samples with DX＜0 and larger values of |DY| are always n-type conducting, and sample with DX>0 and DY>0 are always p-type conducting. In addition, as DX<0 and DY<0, the dominant defect pair calculated from the point defect model is VCu and InCu, their concentrations varies as a function of DY. Once DY is relatively more negative, [VCu] increase and that forms [VCu]＞[InCu]. Therefore, the electrical conductivity of CuInSe2 changed from n-type to p-type. The Growth model of MBE is considered to investigate the reactive mechanism of epitaxial growth. At 500℃, the BEP of In and Cu molecular beam fluxes supplied were 5×10-8~5×10-7 torr for the MBE growth of CuInSe2 films. The change of Se molecular beam flux not only affect the composition of CuInSe2 films, but also the deviation from molecularity DX and the deviation from valence stoichiometry. As Se molecular beam flux increase to 10-6 torr, the concentrations of dominant defects show to decrease about three orders. Thus, the increase of Se BEP results in increasing the mobility as well as the conductivity. On the whole, this study is based on the simulation to investigate the mechanism of MBE. It could be used to control precisely the composition of CuInSe2 films leading to obtain the electrical characteristics for solar cell design.