TAILIEUCHUNG - Solar Cells Thin Film Technologies Part 4

Tham khảo tài liệu 'solar cells thin film technologies part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Application of Electron Beam Treatment in Polycrystalline Silicon Films Manufacture for Solar Cell 79 The P-doped polycrystalline silicon absorber of 10cm2 was melted and recrystallized by a controlled line shaped electron beam size in 1x100mm2 as described in . The appearance of the sample after recrystallization was shown in . The samples are preheated from the backside to 500 C within 2 min by halogen lamps. The electron beam energy density applies to the films is a function of the emission current density the accelerating voltage and the scan speed. The scan speed is chosen to 8mm s and the applied energy density changes between mm2 and mm2. To obtain the required grain size the silicon should be melted and re-crystallized. Therefore temperature in the electron beam radiation region should be was over the melting point of silicon of 1414 C. The surface morphology of the film as well as distribution of WSi2 phase under different energy densities has been investigated by means of a LEO-32 Scanning Electron Microscopy. Fig. 3. Appearance of polycrystalline silicon absorber after recrystallization 3. Results and discussion Microstructure of the capping layer The applied recrystallization energy density strongly influences the surface morphology and microstructure of the recrystallized silicon film. With the energy increasing the capping layer becomes smooth and continuous and less and small pinholes form in the silicon film. Excess of recrystallization energy density leads to larger voids in the capping layer more WSi2 Si eutectic crystallites a thinner tungsten layer and a thicker tungstendisilicide layer. gives the top view of the polycrystalline silicon film after the recrystallization. The EB surface treatment leads to recrystallization to obtain poly-Si films with grain sizes in the order of several 10pm in width and 100pm in the scanning direction as shown in . The polycrystalline silicon films in are EB remelting .

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