摘要(英) |
Thin-film solar cells have the potential for substantial cost advantage versus traditional wafer-based crystalline silicon because of factors such as lower material use, fewer processing steps, and simpler device processing and manufacturing technology for large-area modules and arrays.
Copper indium gallium selenide (CuIn(1-x)GaxSe2, CIGS) has attracted much attentions for its applications in thin film solar cells. Indium selenide (In2Se3) thin film has been used in Mo/CIS/In2Se3/ZnO solar cell fabrication as a buffer layer and it plays an important role in improving efficiency.
We propose a method to prepare single-phase γ-In2Se3 films by using MOCVD with dual-source precursors, trimethylindium (TMI) and hydrogen selenide (H2Se), to deposit on silicon substrates. The flow rate of these two precursors could be adjusted individually to obtain desired VI/III ratio. Furthermore, the AlN and low temperature In2Se3 layers are used as buffer layer during the growth process, respectively. The crystal qualities of In2Se3 films are much improved by introducing buffer layers. The crystal structure of the γ-In2Se3 films was determined by X-ray diffraction (XRD). It is found that the films are single-phase γ-In2Se3 with defect Wurtzite structure when the growth temperatures are between 350°C to 450°C. The single-phase γ-In2Se3 films that we obtained have strong exciton emissions of 2.14 eV at 20 K. The band gap of single-phase γ-In2Se3 at room temperature is estimated at 1.93 eV. Besides the buffer layer used in CIGS-based solar cells, indium selenide also has potential applications in optoelectronic device fabrications. Another interesting application of indium selenide is in phase-change recording medium.
We also propose a method to prepare CIS/CIGS films by using MOCVD with Cu/Mo-coated soda-lime glass substrates. The precursors of In, Ga and Se are TMI, triethylgallium (TEG) and H2Se, respectively. The copper films react with precursors to form CIS/CIGS films. The structure of CIS/CIGS films was determined by XRD. It is found that the films are at single chalcopyrite phase. The optical bandgap of CIS/CIGS films could be adjusted from 0.6 eV to 1.4 eV by changing the growth conditions. Therefore, the tandem cell of CIGS-based solar cells can be fabricated by using this technique and may improve the conversion efficiency over 25% in the future.
In this thesis, we demonstrate new techniques of growing In2Se3 and CIS/CIGS films. The high quality In2Se3 buffer layers and CIS/CIGS films have been successfully prepared by using MOCVD methods. Thus, the development of CIGS-based solar cells and related devices can easily be achieved by using MOCVD technique with a single in-line process. |
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