tailieunhanh - Solar Cells Thin Film Technologies Part 6

Tham khảo tài liệu 'solar cells thin film technologies part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Crystalline Silicon Thin Film Solar Cells 139 thermal annealing step at 900 C follows. The silicon layers are passivated by a hydrogen plasma treatment. Finally rather demanding structuring and contacting processes follow. In production modules m2 in size reached about 7 efficiency. In the lab efficiency were achieved on 92 cm2 minimodules Keevers et al. 2007 . The production was stopped probably because of the high cost PECVD deposition which was used because the method was the only one available for silicon deposition in the m2 range. In the lab high rate electron beam evaporation was tested as an alternative which delivered minimodules with the efficiency of similar to that of the industrially produced modules Egan et al. 2009 Sontheimer et al. 2009 . The grain size originating in the furnace anneal is dictated by the interplay of crystal nucleation within the amorphous matrix and growth of the nuclei see Sect. 5 . One can influence both processes by the temperature of the annealing step. Practically however there is not much choice. At lower temperature the annealing time required for complete crystallization would reach unrealistic high values so that this is not possible in production. Higher temperatures are not endured by the glass substrate for the time span needed for crystallization. Even at 600 C 18 h are required for crystallization and high temperature resistant borosilicate glass has to be used instead of a much cheaper soda lime glass. As an alternative for the furnace crystallization pulsed excimer laser crystallization via the melt is a process industrially used in flat panel display production. For this application however rather thin films 100 nm are required and the resulting grain size is rather small typically below 1 pm. In the context of solar cell preparation requiring films thicker than 1 pm this method has been mentioned only rarely Kuo 2009 . 3. Multicrystalline silicon thin film solar cells grains 10 ụm Basic .