GaAs基底TiO2/SiO2减反射膜的反射率性能分析

本文设计并制备了适用于砷化镓(GaAs)多结太阳电池的TiO2/SiO2双层减反射膜,通过实测反射谱来验证了理论设计的正确性。利用编程分析了TiO2、SiO2单层膜的厚度及其折射率对双层膜系反射率的影响。结果显示,在短波范围(300～600 nm),TiO2膜厚对反射率的影响要大于SiO2,而SiO2折射率对反射率的影响比TiO2大;在中波范围(600～900 nm),随着单层膜的厚度和折射率的增加,双层膜系反射率存在一个最小值,变化趋势是先降低,而随后增加。同时,计算结果得到SiO2和TiO2的最优物理膜厚分别为78.61 nm和50.87 nm,此时在短波段中心波长λ1=450 nm处最小反射率为0.0034%,在中波段中心波长λ2=750 nm处最小反射率为0.495%。采用电子束蒸发法在GaAs基底上淀积TiO2/SiO2双层膜,厚度分别为78 nm和50 nm。实测短波和中波相应的反射率极小值分别为0.37%和2.95%,与理论结果吻合较好。

Analysis of Reflectance Performance of TiO2/SiO2 Antireflection Coating on GaAs Substrate

TiO2/SiO2 double-layer antireflection coatings of GaAs multi-junction solar cells was designed and fabricated.The validity of theoretical design was further verified.The influence of TiO2 and SiO2 layer thickness and refractive index on the reflectance of film system was analyzed.The results showed that film thickness of TiO2 is greater than SiO2 on the reflectance in the short wavelength(300-600 nm),but the refractive of SiO2 is greater than TiO2 on the reflectance.At center wavelength(600-900 nm),as the single-layer film thickness and refractive index increasing,reflectivity of bilayer system has a minimum,the trend is to reduce and increase subsequently.Simultaneously,the optimal physical thickness of SiO2 and TiO2 is 78.61 nm and 50.87 nm respectively by programming calculation.Then the minimum reflectance of 0.0034% was obtained at center wavelength λ1=450 nm in the short wavelength and the minimum reflectance of 0.495% was obtained at center wavelength λ2=750 nm in the middle wavelength.TiO2/SiO2 double-layer coatings were deposited on GaAs substrate by electron beam evaporation and the physical thickness is 78.61 nm and 50.87 nm respectively.Practical minimum reflectance is 0.37% at λ1=449 nm and 2.95% at λ2=748 nm,which is close to theoretical value.