Research Of Laser-doped Selective Emitter For Crystalline Silicon Solar Cells

Laser doping selective emitter technology is one of the important methods to improve conversion efficiency of photovoltaic cells. In this paper, diffusion model and laser doping model are built theoretically. Laser doping experiments is conducted, and the mechanism of how elective emitter technology improves the conversion efficiency of photovoltaic cells is analyzed. The main contents of this paper include:(1) The analysis of the features and advantages of the selective emitter structure compared with traditional battery structure and the discussion about the mechanism of how selective emitter technology improves the open circuit voltage, short circuit current, the fill factor, the spectral response and the conversion efficiency of the cell.(2) Diffusion model is built theoretically. The interactions of laser and crystal silicon are researched based on the heat conduction theory, and the heat source model, weld crater model and sheet resistance model are built, so the parameters of the design, which for the distribution of sheet resistance in the emitter region and electrode areas of selective emitter solar cell, are optimized.(3) Laser doping selective emitter experiment is conducted based on the existing solar cells manufacturing technology. Nanosecond pulsed laser with a wavelength of 532 nm was used to conduct laser doping on crystalline silicon wafers which remains phosphosilicate glass after diffusion. The sheet resistance decreased about 50%, and with the increasing of laser power, the sheet resistance decreased more significantly. The external quantum efficiency of the laser-doped solar cells was tested and is improved by 18% to the highest in the short wavelength band compared to conventional solar cells. The photoelectric conversion characteristics of laser-doped polycrystalline silicon cells were studied, and the conversion efficiency of the battery has improved by an average of 0.15%-0.34%.(4) When the laser working current is too large, it's easy to cause the battery failure and reduce the yield of battery. The shape of heavily doped region and laser doping mask are designed in order to solve this problem. It can not only improve the yield of battery, but also can improve the efficiency of laser doping.The results of laser doping experiment in this paper show that: sheet resistance of the battery, the external quantum efficiency and conversion efficiency are improved by laser doping technique. Therefore, it has certain reference value for high efficiency selective emitter solar cells industrialization.