水热条件下生长FeS2-Fe1－xS异质结构的光吸收特征研究

摘要

Fe-S series ,especially FeS2 and Fe1 - x S is the main component of crustal rocks as important metal sulphides .Pyrite (FeS2 ) shows a promising vision in solar cell materials for its high absorption coefficient and suitable band gap .Predecessors have done some researches on the photovoltaic properties of Fe-S series under different conditions .However ,little researches have been done on the coexisted sulphide of FeS2 and Fe1 - xS .FeS2 and Fe1 - xS often appear as symbiotically due to their similar formation conditions .So the study on the optical absorption characteristics of FeS2 and Fe1 - x S are of important significance .In order to study the optical absorption characteristics of FeS2-Fe1 - x S heterostructures ,using the SEM and XRD to characterize the morphology ,composition and structure ,respectively .The results show that the samples were cubic pyrite with a certain amount of pyrhotite (Fe1 - xS) .The crystal partical size was between 5 and 10 nm .Measurement of the absorption spectrum was per-formed using Cary 500 UV-Vis-NIR spectrophotometer ,acquiring the results of 1 860~1 889 nm ,and the absorption peak in 1879nm .According to the band gap (eV) formula ,the band gap value is calculated to be 0.657 8 eV .The extreme electrical-to-optical conversion efficiency achieved was about 15% .By the first principles ,we analysed the reason of the changing of the band gap value ,and then compared the result with previous one .The internal structure of mineral is the important factor affecting the photoelectric conversion .The light absorption characteristics of FeS2-Fe1 - x S heterostructures synthesized under hydrothermal conditions is better than the characteristics from natural pyrite with defects of Co and Ni .The heterostructures can improve the electrical-to-optical conversion efficiency and provide scientific basis for the absorption characteristics research of Fe-S series ma-terials .%铁硫系列矿物是重要的金属硫化物，FeS2和Fe1－ x S分别是铁硫系列矿物的重要成员。其中黄铁矿（FeS2）具有较大的吸收系数及合适的禁带宽度，适用于做太阳能电池材料，具有较好的应用前景。前人对不同条件下的铁硫系列矿物光伏特性进行了一定的研究，但对于 FeS2和Fe1－ x S共存情况下光吸收性能研究较少。FeS2和Fe1－ x S分别是铁硫系列矿物的重要成员，由于形成条件较为接近，常共生出现。因此，对FeS2和Fe1－ x S光吸收性能的研究具有重要意义。以水热条件下合成微米粒状FeS2-Fe1－ x S为样本，分别使用SSX-550扫描电子显微镜、多晶X射线衍射仪（XRD）观测表征粉末晶体的形态、成分和结构。结果表明：所测样品主要为FeS2中立方晶系黄铁矿，含有一定量的斜方晶系磁黄铁矿（Fe1－ x S ），样品平均粒度在5～10μm左右。用Cary500型紫外-可见近红外分光光度计在200～2000 nm范围内测出了样品的吸收谱介于1860～1889 nm之间，吸收峰值为1879 nm。根据带隙（eV ）公式计算样品的禁带宽度为0.6578 eV ，对应的“极限转换效率”可达到15％左右，利用第一性原理分析样品禁带宽度变化的原因，并与前人研究结果进行对比。分析认为：矿物内部结构是影响光电转化的重要原因，所合成具有FeS2-Fe1－ x S异质结构材料的光吸收特性，较天然地质体中含Co和Ni缺陷的黄铁矿光吸收特性好，光电转换效率有所提高，为深入研究Fe-S系列材料的光伏性能提供了科学依据。