The Fabrication Of Nanostructuredthin Films Electrode Materials And Their Applications In CIGS Thin Film Photovoltaic Devices

As a clean and renewable energy sources, solar cells are considered to be one of the most effieicent strategies to resolve the probolems of energy e Xhaustion and environmental pollution. Nowadays, the development and utilization of solar cells are ganing considerable concern increasingly.Compared to wafer-based silicon solar cells, thin film solar cells take the advantage of low cost in materials utilization, which is favorable to the industrial production.Among all the thin film solar cells, polycrystalline CIGS absorber materials have been considered as one of the most promising candidates for the manufacturing of low-cost thin film photovoltaics. New record power conversion efficiency(PCE) above 20% has been achieved on the laboratory scale for CIGS thin film solar cells. However, there is still a tradeoff between the absorption and the collection of photo-generated carriers in the CIGS thin film solar cells due to its film nature.There is still room for further improvement of its performances. As we know,nanostructures have the advantage of large specific surface area and the antireflective properties. When all of the material properties of CIGS thin solar cells have been optimized, the integration of ordered micro/nanostructure materials in thin film solar cells is considered as one of the most promising ways to resolve the contradiction between light absorption and the collection of carriers in CIGS thin film solar cells.In this paper, the back electrode of Mo thin films and ZnO/AZO window layers in CIGS thin film solar cells have been fabricated by magnetron sputtering and have been investigated systematically. Based on the optimized thin film electrode materials with high quality, ordered Mo, ZnO nanostructures were facricated through the nanosphere lithography(NIL) technique. The influences of these nanostructures on the CIGS solar cells wereinvestigated.Mainly, three parts of research works were carried out in this paper.(1) Fabrication of Mo thin film and Mo nanostructures and their applications in CIGS solar cell:Molebdenum(Mo) thin films were deposited on well-cleaned soda-lime glass substrates using DC magnetron sputtering.Their electrical, structural and morphological properties were analyzed to investigate the effects of Ar pressure, deposition power, deposition time and the rotating speed of substrate. The Mo films with e Xcellent adhesion and low resistance were obtained by two-step sputtering. The square resistance of the Mo films was 0.3??□.The Mo film was used as the back electrode of the CIGS solar cell,the efficiency of the CIGS solar cell e Xceeded 10%. The large-scale ordered Mo nanostructures were fabricated through the nanosphere lithography technique combined with the magnetron sputtering. Also, the Mo nanostructureswere introduced to the CIGS solar cells and the effects of Mo nanostructures on the performances of CIGS solar cells were investigated.(2) Highly transparent and conductive Al-doped ZnO thin films deposited by RF magnetron sputtering:AZO films have been deposited on glass substrate by radio frequency(RF) magnetron sputtering. The influences of substrate temperatures on morphological, structural, optical and electrical properties of AZO films were systematically investigated. The results indicate that all AZO films have the he Xagonal structure with c-a Xis preferred orientation. Morphological and electrical measurements have revealed that the substrate temperatures have strong influences on the microstructure, optical and electrical properties of AZO films. The AZO film is highly transparent from ultraviolet to near infrared range with highest average transparency e Xceeding 83%. The minimum resistivity is as low as 6.1′10-4 ?·cm, the carrier concentration and mobility are as high as 3.357′1020 cm-3 and 30.48 cm2/Vs, respectively. These properties are comparable to or e Xceed the reported values of ZnO based transparent conducting o Xide films, which meet the requirement for practical applications as the transparent electrode in the thin film solar cells.(3) Fabrication of ZnO thin films and ZnO nanostructures and their applications in CIGS solar cells:ZnO thin films were deposited on well-cleaned soda-lime glass substrates using RF magnetron sputtering.Their electrical, structural and morphological properties were analyzed to study the effects of Ar pressure, deposition power and deposition time. The thickness and the transparency are 50 nm and 85%, respectively. The resistance of the ZnO film is greater than 1000MW. The ZnO film was used as the top electrode of the CIGS solar cell, the efficiency of the CIGS solar cell has attained 10.39%.Large-scale patterned microbowl-like and volumetric flask-like ZnO cavites were fabricated through the versatile colloidal lithograhpy technique combined with the hydrothermal growth reaction. The patterned ZnO cavities with micorbowl-like or volumetric flask-like structures can be easily controlled by the hydrothermal growth time. The ZnO cavites with different periodicity showed distinct optical properties, which were investigated by UV–visible absorption and photoluminescence spectroscopies.