Analysis of Aluminum - induced Crystallization and Vacuum Deposition of Polycrystalline Silicon Films

As thin film solar cell technology can effectively reduce the consumption of silicon materials, thereby greatly reducing costs, but also to ensure conversion efficiency, it has become the focus of today's scientific research and photovoltaic industry. Cu-indium-selenium thin films have been considered as the ideal photovoltaic material, the efficiency of the battery can reach 15%. However, its preparation process requires precise control of the main semiconductor process parameters and raw materials seriously restricts its production and development. Cadmium telluride thin film solar cells in the visible light of a very high absorption coefficient, the solar cell conversion efficiency can reach more than 10%, but cadmium is a toxic element in the production and use of the process will adversely affect the environment. Amorphous silicon thin film with a relatively strong absorption of light, the battery just a few microns thick, but the phenomenon of its light-induced recession is very serious, greatly reducing people's enthusiasm for it. Polysilicon film can overcome the shortcomings of the above several films, thus becoming the focus of the current research and future development trend.

At present, polysilicon thin film commonly used preparation methods plasma enhanced chemical vapor deposition, hot filament chemical vapor deposition, excimer laser crystallization, solid phase crystallization, rapid heat treatment. In the present study, amorphous silicon thin films were fabricated by vacuum evaporation method, and the crystalline silicon films were obtained by multi-solar photovoltaic pumps. Compared with other methods, the method has the characteristics of simple process, low crystallization temperature, short crystallization time, high crystallization rate and large grain size. The effects of substrate distance, substrate temperature and annealing temperature on the surface morphology, grain size and distribution, and crystallization rate of the films were investigated by means of atomic force microscopy and Raman spectroscopy.

Experimental raw materials for the purity of 99.99% of the polysilicon powder. The resistance evaporation source is a high-purity graphite sheet with a size of 80 mm x 5.8 mm x 1.7 mm. Using ordinary glass as the substrate, first with deionized water, then, respectively, with acetone, ethanol, ultrasonic cleaning 5min, and finally washed with deionized water, the surface of the dish drying. A layer of amorphous silicon film was deposited on the surface of the glass substrate by a DM-450A vacuum coating machine, and a relatively thin aluminum film was deposited on the surface of the amorphous silicon film. Several samples were prepared by adjusting different processing parameters . The samples were placed in a box resistance furnace and annealed at 300-500 ° C for a certain time. The samples were etched in a standard aluminum etch bath to remove residual aluminum from the surface.

A thin film of amorphous silicon was deposited on the glass substrate by vacuum evaporation. The grain size distribution was more uniform and the grain size was 0.5-5μm. The crystallization rate was 89% by aluminum-induced crystallization. Polycrystalline silicon thin film. The substrate distance has a significant influence on the surface topography of the thin film. The output power of the moderate PV module is calculated from the uniform distribution of the film grain, the surface flatness is good and the film thickness is larger. Substrate temperature and annealing temperature have significant influence on the crystallization rate of the films. Under the experimental conditions, the crystallization rate of the films increases with the substrate temperature. With the increase of the annealing temperature, the crystallization rate of the films increases , When the temperature reaches 500 ℃, the crystallization rate reaches the maximum value of the solar street lamp in Henan Province, the annealing temperature is further increased, the crystallization rate of the film is reduced.