掺杂非晶氧化硅薄膜中三元化合态与电子结构的第一性原理计算  

First principle study of ternary combined-state and electronic structure in amorphous silica

作　　者：万亚州 高明 李勇[1] 郭海波 李拥华[1] 徐飞[1] 马忠权[1,3] Wan Ya-Zhou Gao Ming Li Yong Guo Hai-Bo Li Yong-Hua Xu Fei Ma Zhong-Quan(SHU-SolarE R＆D Lab, Department of Physics, College of Sciences, Shanghai University, Shanghai 200444, China School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China Instrumental Analysis and Research Center, Shanghai University, Shanghai 200444, China)

机构地区：[1]上海大学理学院物理系,索朗光伏材料与器件R&D联合实验室,上海200444 [2]上海大学材料科学与工程学院,上海200444 [3]上海大学分析测试中心,上海200444

出　　处：《物理学报》2017年第18期284-290,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61674099,61274067,60876045);索朗光伏材料与器件R&D联合实验室基金(批准号:SSE0700601)资助的课题~~

摘　　要：基于密度泛函理论和分子动力学方法,研究了ITO-SiO_x(In,Sn)/n-Si异质结光伏器件中非晶SiO_x层的氧化态和电子结构.计算结果表明:具有钝化隧穿功能的超薄(<2 nm)非晶SiO_x层,是由In,Sn,O,Si四种元素相互扩散形成的,其中In,Sn元素在SiO_x网格中以In-O-Si和Sn-O-Si成键态存在,形成了三元化合物.In和Sn的掺杂不仅在SiO_x的带隙中分别引入了E_v+4.60 eV和E_v+4.0 eV两个电子能级,还产生了与In离子相关的浅掺杂受主能级(E_v+0.3 eV).这些量子态一方面使SiO_x的性能得到改善,在n-Si表面形成与反型层相衔接的p-型宽禁带"准半导体",减少了载流子的复合,促进了内建电场的建立.另一方面有效地降低了异质结势垒高度,增强了ITO-SiO_x(In,Sn)/n-Si光伏器件中光生非平衡载流子的传输概率,促进了填充因子的提升(>72%).In this paper, for the ITO-SiO_x（In, Sn）/n-Si photovoltaic device, the molecular coacervate of In-O-Si bonding and two kinds of quantum states for indium-grafted in amorphous silicon oxide a-SiO_x（In, Sn） layers are predicted by molecular dynamics simulation and density function theory calculation, respectively. The results show that the SiO_x layers are the result of the inter-diffusion of the In, Sn, O, Si element. Moreover, In-O-Si and Sn-O-Si bonding hybird structures existing in the SiO_xlayers are found. From the result of formation energy calculations, we show that the formation energies of such an In-O-Si configuration are 5.38 eV for Si-rich condition and 4.27 eV for In-rich condition respectively, which are both lower than the energy（10 eV） provided in our experiment environment. It means that In-O-Si configuration is energetically favorable. By the energy band calculations, In and Sn doping induced gap states（E_v＋4.60 eV for In, E_v＋4.0 eV for Sn） within a-SiO_2 band gap are found, which are different from the results of doping of B, Al, Ga or other group-Ⅲ and Ⅴ elements. The most interesting phenomena are that there is either a transition level at E_v＋0.3 eV for p-type conductive conversion or an extra level at E_v＋4.60 eV induced by In doping within the dielectric amorphous oxide（a-SiO_x） model. These gap states（GSII and GSIS） could lower the tunneling barrier height and increase the probability of tunneling, facilitate the transport of photo-generated holes, strengthen the short circuit current, and/or create negatively charged defects to repel electrons, thereby suppressing carrier recombination at the p-type inversion layer and promoting the establishment of the effective built-in-potential, increasing the open-circuit voltage and fill factor. Therefore, the multi-functions such as good passivation, built-in field, inversion layer and carriers tunneling are integrated into the a-SiO_x（In, Sn） materials, which may be a good candidate for the selective contac

关 键 词：非晶SiO_x层 密度泛函理论 异质结太阳电池 量子隧穿 

分 类 号：O469[理学—凝聚态物理]