Study On The Fabrication Of Multi-crystalline Silicon PERC Solar Cell And Its Light Induced Degradation Effect

With the development of technology,the price of multi-crystalline silicon wafers has greatly been reduced after the application of diamond wire saw technology.However,the efficiency of multi-crystalline silicon solar cells has stagnated,which is limited to about 19%.Meanwhile,the efficiency of mono-crystalline silicon solar cells has exceeded 22%with the application of PERC?passivated emitter and rear cell?technology.In order to improve the competitiveness of multi-crystalline silicon solar cells and further reduce the cost of multi-crystalline silicon solar cells,the front side and rear side of multi-crystalline silicon solar cells were optimized in this thesis by using PERC technology,and its light induced degradation effect was explored.In this thesis,the front side of multi-crystalline silicon solar cells was optimized.Metal assisted chemical etching method was taken to make surface texture of multi-crystalline silicon,and the anti-reflection structure of multi-crystalline silicon surface is optimized.The properties of multi-crystalline silicon solar cells were investigated by sequentially depositing double-layer silicon nitride and a layer of silicon oxide on the surface of multi-crystalline silicon through PECVD method.Meanwhile,a thin layer of silicon oxide was grown on the surface of multi-crystalline silicon by thermal oxidation to improve its passivation properties.The optimal treatment conditions of different coatings were obtained.Secondly,the back structure of polycrystalline silicon solar cells was optimized.SiN_x and Al₂O₃were deposited by PECVD and ALD respectively,to passivate the rear side and improve the conversion efficiency of multi-crystalline PERC solar cells.The polishing process of rear side was optimized and the laser process was added to match the PERC technology.An efficiency of 19.94%of multi-crystalline PERC solar cells was achieved.Finally,the light induced degradation of multi-crystalline PERC solar cells was explored.It was found that the light induced degradation of multi-crystalline PERC solar cells obviously decreased with the increase of sintering temperature.Despite that the light induced degradation of multi-crystalline PERC solar cells could be restrained by reducing the sintering temperature,a suitable low-temperature silver paste matching the process was still needed.In addition,the multi-crystalline PERC was regenerated by electro-injection annealing.An increase of 0.83%of conversion efficiency of multi-crystalline PERC could be achieved with an injection current of 8.0A,an annealing temperature of 260?and a treating time of 2 hours.The decrease of conversion efficiency caused by light induced degradation under 5h illumination was only 0.61%and was only 0.3%when using the gallium-doped multi-crystalline silicon wafer.