n型IBC太阳电池选择性发射极工艺研究

Selective Emitter Technology of n-Type IBC Solar Cells

为提升n型叉指背接触(IBC)太阳电池的光电转换效率,采用丝网印刷硼浆和高温扩散的方式形成选择性发射极结构,研究了硼扩散和硼浆印刷工艺对电池发射极钝化性能和接触性能的影响。实验结果表明,在硼扩散沉积时间和退火时间一定的条件下,硼扩散通源(BBr_(3))流量为100 mL/min,沉积温度为830℃,退火温度为920℃时,发射极轻掺杂(p^(+))区域的隐开路电压达到710 mV,暗饱和电流密度为12.2 fA/cm^(2)。发射极局部印刷硼浆湿重为220 mg时,经过高温硼扩散退火,重掺杂(p^(++))区域的隐开路电压保持在683 mV左右,该区域方块电阻仅46Ω/□,金属接触电阻为2.3 mΩ·cm^(2).采用该工艺方案制备的IBC电池最高光电转换效率达到24.40%,平均光电转换效率达到24.32%,相比现有IBC电池转换效率提升了0.28个百分点。

In order to improve the photoelectric conversion efficiency of n-type interdigitated back contact(IBC)solar cells,the selective emitter structure was prepared by screen printing boron paste and high temperature diffusion,the effects of boron diffusion and screen printing on the passivation and contact properties of the cells were studied.The experimental results show that when the deposition time and annealing time of boron diffusion remain unchanged,the BBr_(3) flow rate is 100 mL/min,the deposition temperature is 830℃,and the annealing temperature is 920℃,the implied open circuit voltage of light doping emitter(p^(+))reaches 710 mV,and the dark saturation current density reaches 12.2 fA/cm^(2).When the consumption of the locally printed boron paste at the emitter is 220 mg,after high temperature annealing on boron diffusion,the implied open circuit voltage of heavily doping emitter(p^(++))remains at about 683 mV,the sheet resistance is only 46Ω/□,and the metal contact resistance is 2.3 mΩ·cm^(2).The highest photoelectric conversion efficiency and average photoelectric conversion efficiency of IBC cells prepared by this process are 24.40%and 24.32%,compared with the IBC cells before optimization,the conversion efficiency is improved by 0.28 percentage points.