硅锗量子阱结构在硅异质结太阳电池中应用的数值模拟  

Numerical simulation of silicon heterojunction solar cells with Si/Si_(1-x)Ge_x quantum wells

作　　者：张晓宇[1,2] 张丽平[2] 马忠权[1] 刘正新[2] 

机构地区：[1]上海大学理学院,上海200444 [2]中国科学院上海微系统与信息技术研究所,上海201800

出　　处：《物理学报》2016年第13期304-310,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61204005)资助的课题~~

摘　　要：利用半导体工艺和器件仿真软件silvaco TCAD(Technology Computer Aided Design),模拟研究了采用硅/硅锗合金(silicon/silicon germanium alloy,Si/Si_(1-x)Ge_x)量子阱结构作为吸收层的薄膜晶体硅异质结太阳电池各项性能.模拟结果显示,长波波段光学吸收随锗含量的增加而增加,而开路电压则因Si_(1-x)Ge_x)层带隙的降低而下降.锗含量为0.25时,短路电流密度的增加补偿了开路电压的衰减,效率提升0.2%.氢化非晶硅/晶体硅(a-Si:H/c-Si)界面空穴密度以及Si_(1-x)Ge_x)量子阱的体空穴载流子浓度制约着空穴费米能级的位置,进而影响到开路电压的大小.随着锗含量增加,a-Si:H/c-Si界面缺陷对开压的影响降低,Si_(1-x)Ge_x)量子阱的体缺陷对开压的影响则相应增加.高效率含Si_(1-x)Ge_x)量子阱结构的硅异质结太阳电池的制备需要a-Si:H/c-Si界面缺陷的良好钝化以及高质量Si_(1-x)Ge_x)量子阱的生长.Heterojunction with intrinsic thin-layer（HIT） solar cells attract attention due to their high open circuit voltage and stable performance. However, short circuit current density is difficult to improve due to light losses of transparent conductive oxide and hydrogenated amorphous silicon passivation（a-Si：H） layer and low absorption coefficient of crystalline silicon（c-Si）. Silicon germanium alloy（Si/Si_（1-x）Ge_x）） quantum wells and quantum dots are capable of improving low light utilization by strong optical absorption in the infrared region. In this article, opto-electrical performances of the HIT solar cells integrated with Si/Si_（1-x）Ge_x）quantum wells（HIT-QW） as a surface absorber are investigated by numerical simulation with Technology Computer Aided Design（TCAD）. The influences of germanium content on the electrical performances of HIT solar cells with long carrier lifetimes of Si_（1-x）Ge_x）layers（τ＊p） and defect-free a-Si：H/cSi interface are investigated at first. The simulation results indicate that optical utilization in the infrared region is enhanced with the increase of germanium fraction, while open circuit voltage degrades due to the decreasing of the energy band gap of Si_（1-x）Ge_x）, radiative recombination and auger recombination mechanism in the Si/Si_（1-x）Ge_x）quantum wells. And the conversion efficiency reaches a maximum value at a germanium fraction of 0.25 then drops distinctly.When the germanium fraction increases from 0 to 0.25, the short circuit current density increases from 34.3 m A/cm2 to 34.8 m A/cm2, while the open circuit voltage declines from 749 m V to 733 m V. Hence, the conversion efficiency increases from 21.5% to 21.7% due to the fact that the enhancement of short circuit current density compensates for the reduction of open circuit voltage. When the germanium content increases to more than 50%, a serious open circuit voltage loss of more than 130 m V associated with the energy band gap loss of Si_（1-x）Ge_x）

关 键 词：Si/Si1-xGex量子阱 异质结太阳电池 界面复合 a-Si:H/c-Si 

分 类 号：O471.1[理学—半导体物理] TM914.4[理学—物理]