Polysilicon Suede Preparation And Application To Solar Cells

Now one of the effective ways to lower the cost of the commercial solar cell is to improve the efficiency of the solar cell at present. Although the efficiency of the multi-Si solar cell is lower than that of mono-Si solar cell, the multi-Si material has lower cost, so it has more potential to reduce the cost and it still will be the mainstream of the solar cell market for quite a long time in future. Surface texture is one of the key techniques to improve the efficiency of multi-Si solar cell, and it is also a problem which has not solved very well in industry. It is a urgent problem to find a cost-effective and simple surface texture technique which can be used to improve the efficiency of multi-Si solar cell. According to these ideas, this paper studies the texturing of large-area multi-Si(100mmx100mm) wafer and the possibility of using in multi-Si solar cell.1. The texturing of multi-Si solar cell(also called porous silicon, PS) This work is based on the experience of former postgraduate and the etching solution has high HF concentration and low HNO3 concentration.(1) The relation between etching condition and morphologyThe acid etching method used in this paper can form a homogenous surface texture on large-area multi-Si wafers and its morphology is similar to that of small-area texture. Changing etching condition such as the mixture ratio of etching solution and reaction time in a small range, the textures have similar morphology and this is very useful to its application to industry. If the reaction is acute, it is tend to form larger size morphology and it is difficult to control the reaction. This has relation to the temperature of etching solution.(2) Reflectance characteristicsThe reflectance of large-area texture can low to 5.25% and has unconspicuous selectivity to incidence light during 300nm~1000nm wavelength. In the same Si wafer with that kind of texture different location has similar reflectance, that is to say,the uniformity of itself is good.(3) Composition of PS layerThe main composition of PS layer is silicon, next is oxygen, and it also has little carbon and nitrogen. According to the theory, there should have hydrogen, because of the limit of test measure, it does not detected.2. The application of multi-Si texture in solar cellUsing conventional production technologies, we applied this technique to multi-Si solar cell and the efficiency of our best sample is 6%.The experiment proved that this etching method is compatible with the production technologies now used in industry. If we modify some technology such as selective diffusion process and rapid thermal process(RTP),the efficiency may be improved to 9~10%.