Research On Processes And Technologies For HIT Solar Cells

A underlying cheap alternative to c-Si solar cells are thin film silicon basedheterojunction with intrinsic thin-layer (HIT) solar cells, consisting of hydrogenatedamorphous silicon (a-Si:H). The outstanding advantages of HITs are simple structure, simpleprocess, high efficiency, high stability and low cost.In this paper, the fabrication technologies of the a-Si:H layers, P-doped a-Si:H,texturization and rounded process in HIT solar cells have been studied in details; Effect ofdifferent a-Si:H layers thickness and hydrogen plasma treatments on main photovoltaicparameters have been studied in simple. In order to achieve high-efficiency HIT solar cells,the best fabrication technologies have been obtained.The a-Si:H layers and P-doped a-Si:H in HIT solar cells were fabricated by plasmaenhanced chemical vapor deposition (PECVD). The growth rate, optical band gap, darkconductivity of the amorphous silicon films and the performance of the HIT solar cellsprepared in different PECVD parameters have been measured and analyzed. The bestdeposition parameters for a-Si:H layers are350℃substrate temperature,20%SiH4concentration and4W RF power; for P-doped a-Si:H layers are350℃substrate temperature,1%B2H6/SiH4and8W RF power. The best thickness for a-Si:H layers is3.3nm. Theefficiency of the HIT solar cells reached15.56%with the best deposition parameters.Before deposition, the silicon substrate was treated by hydrogen plasma. In order toachieve the best passivation, the hydrogen plasma treatments need to sustain for40s.The silicon substrate was corroded in alkaline solution. The effect of corrosiontemperature, IPA concentration, NaOH concentration and corrosion time on the reflectanceof the silicon substrate were analyzed. The best surface morphology was obtained at80℃，3vol%IPA，1.1wt%NaOH，22.5min，0.3vol%additives. Uniform pyramid structure wasobserved. The average surface reflectance from400-1100nm was11.68%. The base width ofpyramid was about2–4μm. The textured silicon substrate was corroded in acidic solution. The effect of corrosiontime on the reflectance and the surface morphology of the silicon substrate and theperformance of HIT solar cells were analyzed. The best corrosion time was60s. All aspectsof HIT solar cell were improved with the optimized texturization and rounded process.