低效纳米孔晶体硅太阳电池性能研究

Property Research on the Low Efficiency Nano Porous Silicon Solar Cells

晶体硅太阳电池生产中,降低表面反射率能够提高太阳电池短路电流和转换效率.纳米孔硅的表面反射率极低,但报道中所实现的太阳电池输出参数(开路电压、短路电流、填充因子)都低于金字塔结构表面.采用对比法从光学性能、表面微结构和电极接触上对纳米孔硅和金字塔太阳电池进行比较分析,来研究纳米多孔硅太阳电池转换效率的抑制因素.研究表明短时间腐蚀的纳米孔硅太阳电池表面沉积氮化硅钝化膜后的平均反射率提高.长时间腐蚀的纳米孔硅表面沉积氮化硅后在短波段的反射率极低,因此平均反射率小于金字塔结构表面.但是由于纳米孔硅太阳电池的表面复合率高,而孔壁上附着的毛刺不仅会进一步增大表面复合,还会削弱表面钝化效果,因此短波段激发的光生载流子难以被太阳电池利用.所以,光利用和表面复合是抑制纳米孔硅太阳电池开路电压和短路电流的原因,而过大的串联电阻是纳米孔硅太阳电池短路电流和填充因子低的另一个原因.

To date,pyramidal surface structure was currently widely used in silicon solar cells production processes.But the surface reflectance should be reduced to obtain a high short circuit current and conversion efficiency.And nano porous silicon surface was a hopeful candidate due to the surface reflectance is especially low.However,the output performance （open circuit voltage,short circuit current and fill factor） of the nano porous silicon solar cells were lower than that of reference cells （with pyramidal surface）.The disadvantages of nano porous silicon solar cells were studied in this paper and three factors were discussed.One was the surface reflectivity.For the samples that short time etching,surface reflectance would be higher after silicon nitride deposition by plasma enhanced chemical vapor deposition method.If the etching time was prolonged,surface reflectance in the short wavelength range would be lower than that of the pyramidal one,as well as the average reflectance.But the excited carriers were hard to be collected due to the high surface recombination.In addition,burrs were formed during the etching process of nano porous silicon layer.It would further increase the surface recombination and depress the passivation effects.So,optical properties and surface recombination were the two main reasons for the lower conversion efficiency of the cells.And poor contact properties of the electrodes was the third element.