低温生长ITO薄膜及其在太阳电池中的应用

Low-temperature growth of ITO thin films for application in solar cells

氧化铟锡（ITO）同时结合 了可见光范围内高透过率和高电导率等特性,被广泛应 用于Si基薄膜太阳电池中。本文侧重研究了采用反应热蒸发（RTE）技术低温（约160 ℃）生长ITO透明导电薄膜过程中 不同Sn掺杂含量对薄膜微观结构以及光电性能的影响。实验结果表明,随着Sn掺杂含量的增 加,ITO薄 膜微观结构稍有变化,薄膜的电子迁移率呈现先增大后减小的趋势,薄膜的光学带隙一定程 度上呈现展宽 趋势；对于较高的Sn掺杂含量,在低温条件下电离杂质散射和中性杂质散射成为影响电子迁 移率降低的重 要因素。经过薄膜生长优化,较佳的Sn掺杂含量为6.0wt.%,ITO 薄膜电阻率为3.74×10^－4 Ω·cm,电子迁移 率为47cm2/Vs,载流子浓度为3.71×10^20 cm^－3,且在380~900nm波长范围内的平均透过率约87%。将其应用于结构为SS/Ag/ZnO/nip a-S iGe：H/nip a-Si：H/ITO/Al的n-i-p型a-Si：H/a-SiGe：H叠层太阳电池, 取得的光电转化效率达10.51%（开路电压V oc=1.66V,短路电流密度Jsc =9.31mA /cm2,填充因子FF=0.68） 。

Transparent conductive tin-doped indium oxide （In2O3：Sn,ITO） thin f ilms used as anti-reflecting front electrodes in silicon-based thin film solar cells have been prepared by using t he low cost reactive thermal evaporation （RTE） technique at a low growth temperature of ~160℃.The structur al characteristics,optical and electrical properties of the ITO thin films are investigated with changing the Sn doping concentration.It is observed from XRD micro-structural properties tha t these polycrystalline ITO film s change little.Hall mobilities increase continuously from 38cm2/Vs to 47cm2/Vs and then decrease dra matically down to 30.9cm2/Vs for higher Sn-doping concentrations,and the optical band gaps are weakly affected （~4.02eV）.The optimized ITO thin film deposited with the 6.0% of Sn-doping mass concentration exhibits a high avera ge transparency （~87%） in the wavelength range of 380-900nm,a low resistivity of 3.74×10^-4 Ω cm and a high Hall mobility of 47cm2/Vs. Furthermore,a hydrogenated amorphous silicon and silicon-germanium （a-Si：H/a -SiGe：H） double-junction solar cell fabricated with the optimized ITO front electrodes presents a high convers ion efficiency of 10.51%.