【作者】 张秀娟；

【导师】 孟亮；

【作者基本信息】 浙江大学 ， 材料学， 2003， 硕士

【摘要】 FeS₂（pyrite）是一种具有合适禁带宽度（E_g≈0.95eV）和较高光吸收系数(λ≤700nm，α≥5×105cm^-1)的半导体材料，其组成元素储量丰富无毒，在制备太阳能电池时可以以薄膜形式使用，成本较低，与已有半导体材料相比，是一种较有研究价值的太阳能电池材料。 本文采用Fe膜硫化法制备了FeS₂薄膜。在相同的硫化工艺条件下，分别在Si（111）和玻璃基底上制备了不同厚度的FeS₂薄膜，研究了厚度对薄膜组织和光电性能的影响。采用FeS₂/TiO₂复合膜作为太阳能电池光电极制备了溶液太阳能电池测试样品，对电池的光电转换效率进行了测量，研究了厚度对薄膜光电转换效率的影响。在Si（100）、Si（111）、Al、TiO₂及玻璃等五种基底上制备了相同厚度的FeS₂薄膜，研究了基底对薄膜组织结构的影响。 研究结果表明，硫化温度为400℃，硫化压力为80kPa，硫化时间为20h时，Fe膜能充分形成FeS₂。采用Si（111）基底制备FeS₂薄膜时，随着薄膜厚度的增加，禁带宽度和高吸收区的光吸收系数减小。当厚度小于330nm时，随着厚度的增加薄膜晶粒尺寸增加，而晶格常数降低；当膜厚大于330nm时，随着厚度的增加薄膜晶粒尺寸减小，而晶格常数增加。在玻璃基底上的FeS₂薄膜，当薄膜厚度由70nm增加到300nm时，薄膜晶粒尺寸和晶格常数减小。当薄膜厚度由300nm增加到600nm时，薄膜的晶粒尺寸和晶格常数均增加。随着膜厚的增加，FeS₂薄膜的载流子浓度降低，电阻率增加，高吸收区的光吸收系数减小，薄膜趋于p型导电。膜厚小于130nm时，禁带宽度随膜厚的增加而增加，但当膜厚大于130mn时，禁带宽度随膜厚的增加而减小。 对FeS₂／TiO₂复合膜作为太阳能电池光电极制备的溶液太阳能电池测试样品进行了光电转换效率测量，结果表明，随着薄膜厚度的增加，转化效率先下降后上升，其值总体处于较低水平。 对在Si（100）、Si（111）、Al、TiO₂及玻璃基底上制备的330nm厚的FeS₂薄膜进行分析表明，通过改变基底晶体类型能够在一定程度上控制FeS₂薄膜生长的晶浙江大学硕士毕业论文张秀娟:厚度和基底对FcSZ薄膜结构和性能的影响体位向分布。当在51（1 00）、51（1 11）和A]基底上生长，FeS:薄膜可获得（200）择优取向，在Tio:基底上生长可同时获得（200）及（220）择优取向。非晶玻璃基底对薄膜位向分布影响不明显。基底点阵类型不同则与薄膜的界面错配度不同，除可改变薄膜晶体位向的分布，还可导致晶格畸变程度及晶粒尺寸的变化。当基底为非晶结构或界面有较大的错配度时，FeS:晶体取向分布主要受表面能及晶粒优先生长方向控制，薄膜具有较小的晶格畸变及较细的晶粒。当基底为晶态并且界面错配度较小时，FeS:晶体取向分布除受表面能及晶粒优先生长方向控制外，还受界面应变能的控制，此时薄膜易形成较大的晶格畸变及相对粗的晶粒。更多还原

【Abstract】 As a semiconductor material, FeS2 (pyrite) has high optical absorption coefficient ( 5 l05cm-1 for 700nm) and suitable energy band gap (about 0.95eV). These beneficial behaviors can make pyrite a promising candidate as an absorber material in thin film solar cells. Moreover, another advantage of pyrite is that it is composed of nontoxic, abundant elements.Thin films of pyrite with different thickness have been synthesized by annealing iron films in a sulfur atmosphere on Si(111) and glass substrates. Their structural, optical and electrical characteristics have been determined and the effect of the film thickness discussed. The iron films with diffident thickness on both kinds of substrates can be completely converted into pyrite by sulfurating in 80kPa sulfur atmosphere at 400 for 20h. For the pyrite films on Si(111) substrate, the band gap and optical absorption coefficient tend to decrease with increasing film thickness. The grain size of the films rises and the lattice constant reduces when the film thickness increases up to 330nm. However, in the films thicker than 330nm, the grain size decreases and the lattice constant increases with increasing film thickness. For the films on glass substrates, the gram size and lattice constant decrease with the thickness increasing from 70nm to 300nm and increase as the thickness over 300nm. With increasing in the film thickness, electrical resistivity shows a generally rising tendency and carrier concentration and optical absorption coefficient a reducing tendency. The conducting type tends to show n-type when the film is thicker.The FeS2/TiO2 films have been prepared as the photoanode in a photoelectrochemical set-up and their photoactivity also investigated. The photoelectrical conversion efficiency first decreases and then increases with the thickness of the films, and is generally at a rather low level.Pyrite films with 330nm in thickness have been prepared on the substrates of Si(100), Si(111), Al, TiO2 and glass by annealing the iron films in sulfur atmosphere. The crystal structure has been determined and orientation texture discussed for the films. The results show that the texture distribution of the film can be controlled in a certainextent by using the substrate with different crystalline type. The pyrite films prepared on the substrates Si(100), Si(111) and Al have only one preferred orientation (200) while they on the microcrystalline TiO2 substrates share two preferred orientations (200) and (220). There is an insignificant effect of amorphous glass substrates on orientation distribution in the film growth. Various substrates induce different interfacial mismatch between the film and substrate and result in the changes of lattice distortion degree, grain size and texture distribution. The film surface energy and natural orientation of grain growth mainly dominate the resultant distribution of crystal orientation and induce small lattice distortion and fine grains in the film if the substrate is amorphous or has high interfacial mismatch. Besides the film surface energy and natural orientation of grain growth the interface strain energy participates in the domination to the resultant distribution of crystal orientation and tends to induce strong lattice distortion and coarse grains if the substrate is crystalline and has low interfacial mismatch.更多还原