后退火增强氢化非晶硅钝化效果的研究  

Investigation of post-annealing enhancement effect of passivation quality of hydrogenated amorphous silicon

作　　者：陈剑辉[1] 杨静[1] 沈艳娇 李锋 陈静伟[1] 刘海旭[1] 许颖 麦耀华[1] 

机构地区：[1]河北省光电信息材料重点实验室、河北大学物理科学与技术学院,保定071002 [2]光伏材料与技术国家重点实验室、英利集团有限公司,保定071051

出　　处：《物理学报》2015年第19期409-416,共8页Acta Physica Sinica

基　　金：河北省自然科学基金项目(批准号:E2015201203,E2014201063)资助的课题~~

摘　　要：在本征氢化非晶硅(a-Si:H(i))/晶体硅(c-Si)/a-Si:H(i)异质结构上溅射ITO时,发现后退火可大幅增加ITO/a-Si:H(i)/c-Si/a-Si:H(i)的少子寿命(从1.7 ms到4 ms).这一增强效应可能的三个原因是:ITO/aSi:H(i)界面场效应作用、退火形成的表面反应层影响以及退火对a-Si:H(i)材料本身的优化,但本文研究结果表明少子寿命增强效应与ITO和表面反应层无关;对不同沉积温度制备的a-Si:H(i)/c-Si/a-Si:H(i)异质结后退火的研究表明:较低的沉积温度(<175?C)后退火增强效应显著,而较高的沉积温度(>200?C)后退火增强效应不明显,可以确定"低温长高温后退火"是获得高质量钝化效果的一种有效方式;采用傅里叶红外吸收谱(FTIR)研究不同沉积温度退火前后a-Si:H(i)材料本身的化学键构造,发现退火后异质结少子寿命大幅提升是由于a-Si:H(i)材料本身的结构优化造成的,其深层次的本质是通过材料的生长温度和退火温度的优化匹配来控制包括H含量、H键合情况以及Si原子无序性程度等微观因素主导作用的一种竞争性平衡,对这一平衡点的最佳控制是少子寿命大幅提升的本质原因.The excellent surface passivation scheme for suppression of surface recombination is a basic prerequisite to obtain high efficiency solar cells. Particularly, the HIT （heterojunction with intrinsic thin-layer） solar cell, which possesses an abrupt discontinuity of the crystal network at an interface between the crystalline silicon （c-Si） surface and the hydrogenated amorphous silicon （a-Si：H） thin film, usually causes a large density of defects in the bandgap due to a high density of dangling bonds, so it is very important for high energy conversion efficiency to obtain millisecond （ms） range of minority carrier lifetime （i. e. 〉2 ms）. The a-Si：H, due to its excellent passivation properties obtained at low deposition temperatures and also mature processing, is still the best candidate materials for silicon HIT solar cell. Deposition of a transparent conductive oxide （TCO）, such as indium tin oxide （ITO）, has to be used to improve the carrier transport, since the lateral conductivity of a-Si：H is very poor. Usually, ITO is deposited by magnetron sputtering, but damage of a-Si：H layers by sputtering-induced ion bombardment inevitably occurs, thus triggering the serious degradation of the minority carrier lifetime, i. e., a loss in wafer passivation. Fortunately, this damage can be often recovered by some post-annealing. In this paper, however, the situation is different, and it is found that the minority carrier lifetime of ITO/a-Si：H/c-Si/a-Si：H heterojunction has been drastically enhanced by post-annealing after sputtering ITO on a-Si：H/c-Si/a-Si：H heterojunction （from 1.7 ms to 4.0 ms）, not just recovering. It is very important to investigate how post-annealing enhances the lifetime and its physics nature. Combining the two experimental ways of HF treatment and vacuum annealing, three possible reasons for this enhancement effect （the field effect at the ITO/a-Si：H interface, the surface reaction-layer resulting from annealing in air, and the optimization of a

关 键 词：非晶硅 退火 钝化 少子寿命 

分 类 号：TN304.12[电子电信—物理电子学]