【作者】 郭新华；

【导师】 韩杰才；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2018， 博士

【摘要】 世界能源的严重紧缺对开发利用太阳能相关技术提出了新的要求,尤其是半导体材料的光学性能方面。铜锌锡硒(Cu2Zn Sn Se4,CZTSe)的禁带宽度为1.0-1.50 e V,铜锌锡硫(Cu2Zn Sn S4,CZTS)的禁带宽度为1.30-1.50 e V,与太阳能光谱非常匹配,光吸收系数均高达104 cm-1,被认为是极具潜力的太阳能吸收薄膜材料,目前对CZTSe和CZTS制备技术的研究发展迅速,现有工艺存在设备投入成本高、制备过程伴随有毒有害物质的产生并需要回收处理副产物等问题,并且其制备工艺成本均较高。本研究在目前已有溶胶凝胶法基础上,探索了一种设备投入及能源消耗均很低的、以溶胶凝胶法制备CZTSe和CZTS的新工艺。该工艺条件包括:无毒的小分子反应物、反应物直接进行混合并直接涂布、首次采用的250℃非真空退火处理条件。对所制备的CZTSe和CZTS薄膜,进行表面形貌、物相结构及光学性能分析来表征其吸光性能。本研究主要特点如下:(1)反应物成本低:采用了地球上便宜易得的铜、锌、锡和硒/硫元素;(2)工艺步骤简单:同步加入铜、锌、锡和硒/硫,恒温搅拌得到溶胶凝胶前驱体溶液,在非真空、低温(200-250℃)条件下加热干燥制得铜锌锡硒和铜锌锡硫薄膜;(3)环境友好,直接以无毒的硒化物/硫化物作为硒/硫元素的原材料,避免了以硒化氢和硫化氢等有毒媒介导致的环境污染。其论文的主要内容为:(1)以一种新的溶胶凝胶工艺制备CZTSe和CZTS薄膜,并且用不同的反应物来证明该工艺在制备铜锌锡硫族薄膜具有一定的通用性;(2)分析表征薄膜的光学性能指标,从紫外可见光到红外光谱的不同光谱范围内表征薄膜是对太阳光具有吸收性的光吸收性薄膜。文中先以有机小分子醋酸铜、醋酸锌和无机小分子氯化铜、氯化锌为反应物,分别以无毒的亚硒酸钠、硒酸钠为硒源,在玻璃衬底上制备四种薄膜并分析其光学性能,发现四种薄膜在可见光紫外区域得到的带隙宽度在1.20-1.60e V之间,适宜作为光电转化所需的光吸收性薄膜。拉曼光谱和光致发光光谱分析表明,制得的四种CZTSe薄膜均不发生散射和光致发光作用,即从紫外区域扩大到更宽的光致发光光谱范围内均显示其适宜作为光吸收性材料。这其中CZTSe薄膜在紫外可见光谱范围内的最佳带隙宽度为1.48 e V,满足目前光电转化中需求的光吸收层,未来还可扩大到红外光谱范围内利用该薄膜的光吸收性。接下来以(CH3COO)2Cu·H2O、(CH3COO)2Zn·2H2O、Sn Cl2·2H2O及Zn S小分子试剂为反应物,仍以前述的溶胶凝胶工艺法制备无毒硫化条件下的低成本CZTS,制得具有细小晶体颗粒的表面光滑致密的薄膜。光谱分析发现:在可见光400-1100 nm范围内,CZTS薄膜带隙宽度为2.32 e V;不存在光退激现象带来的反射光,无荧光性;无拉曼散射作用。在2.5-15μm红外光谱区域,薄膜也显示光吸收性。即该薄膜从可见光到红外光谱范围内均呈现出光吸收作用。钙离子掺杂后薄膜的带隙宽度从2.32 e V下降到1.55 e V,成为适宜作为光吸收层的薄膜材料。随后以Cu Cl2·2H2O、Zn Cl2、Sn Cl4·5H2O及Zn S为反应物,同样以上述溶胶凝胶工艺制备CZTS薄膜。得到的薄膜具有絮状球形颗粒,形成了利于光吸收的多孔立体网状结构。该富含锌的薄膜具有Cu2Zn Sn S4特征晶体衍射峰。薄膜厚度在5-16μm时,其带隙宽度位于1.51-1.54 e V。厚度为15μm的CZTS薄膜的带隙宽度为1.45 e V,处于太阳能半导体材料最优范围(1.45-1.50 e V)。上述制得的CZTS薄膜在紫外光谱范围内具有适宜的带隙宽度,且扩大到更宽的红外光谱波段范围内也显示出光吸收性,故该CZTS薄膜在从紫外到红外的光谱范围内适宜作为光电应用的光吸收层材料。本文首次以有机和无机小分子试剂及无毒的硒化和硫化物为反应物,以溶胶凝胶新工艺法制得CZTSe和CZTS光吸收性薄膜,表明该工艺在制备铜锌锡硫族薄膜具有一定的通用性。并且该工艺所用的小分子反应物及试剂均是成本低廉的无毒物质,且操作流程简单易行。对制得的CZTS薄膜,除了以常用的带隙宽度和光吸收系数作为衡量指标,本文还首次以拉曼光谱散射、荧光光谱的荧光、光致发光光谱、红外吸收光谱,共同分析表征该薄膜在可见光和红外光谱范围内均具有的光吸收性,为今后CZTSe和CZTS薄膜在宽光谱范围内的光学表征提供一定参考依据。不但可应用在光电转化中,还可以印刷涂层形式应用为光吸收性材料。更多还原

【Abstract】 The global energy shortage and the desire of renewable energy sources make new demand for more efficient and cost effective use in solar energy especially the optical properties of semiconductor materials.There has been a lot of interest in using copper zinc tin selenide(Cu2Zn Sn Se4,CZTSe)and copper zinc tin sulfide(Cu2Zn Sn S4,CZTS)for solar films.The band gap of CZTSe is about 1.0 e V to 1.50 e V and that of CZTS is about 1.30 e V to 1.50 e V,which both closely match the solar spectrum.Because their absorption coefficients are up to 104 cm-1,both CZTSe and CZTS are considered to the most promising new solar energy absorption materials.At present,the technologies for CZTSe and CZTS are under a rapid development.However,the same issues for all these methods are high cost of equipment,toxicity and harmful by-products during the preparing processings.And the processing technologies are more expensive.In this disseration,a new sol-gel procedure for preparing CZTSe and CZTS film is proposed based on the low equipment investment and energy consumption and present sol-gel methods in accordance to the existing problems in the processings.The mild conditions in the processs are included: non-toxic small molecule reaction reagent,reactants directly mixed and coated processing,the non-vacuum wind drying oven heating treatment,250 ℃ low temperature annealing conditions.For the preparation of CZTSe and CZTS films,the surface topography structure and optical performance analysis are used to characterize the absorption performance of this research.The main characteristics of this research are as follows.(1)The method includes inexpensive sources of copper,zinc,tin,and selenium,sulfur,such as copper(II)acetate,zinc acetate,tin(II)chloride,and zinc sulfide for the organic source material of low molecular weight substances,and copper(II)chloride dihydrate,zinc chloride,tin(IV)chloride pentahydrate,and zinc sulfide for the inorganic source material of low molecular weight substances.(2)All of the elements,including copper,zinc,tin,and selenium,sulfur,can be added at the same time,which simplifies the procedures and the processes.If the materials are mixed by a magnetic stirrer,they form a stable sol-gel precursor solution.A dry CZTS films can be prepared with a non-vacuum and at relatively low temperature(200-250oC).(3)Using safe,stable,and non-toxic zinc sulfide as the source of sulfur rather than the traditional,more toxic substances,such as hydrogen selenium and hydrogen sulfide,furthermore this method can avoid environmental pollution.The main content of this disseration are as follows.(1)The research mainly includes that the new sol-gel technology process is proper and universal through the preparation of the CZTSe and CZTS film.(2)And the characterizations of the film optical performances are detailed as follow.It is feasible to be applied in a wider range of light absorption from ultraviolet visible spectral region extended to the infrared region in the future.Firstly,CZTSe films were prepared by using a mild,non-vacuum,sol-gel procedure method from non-toxic selenide source.The organic small molecule Copper(II)acetate,zinc acetate reagents and inorganic small molecule reagents Copper(II)chloride,zinc chloride were used as reactants to prepare CZTSe films.Further,the optical properties of the film properties were analyzed from the differnent spectral effects.Sodium selenite and sodium selenite were the sources to prepare the four kinds of CZTSe films on the glass substrate.The band gaps lied in the range of 1.20 to 1.60 e V from the above four kinds CZTSe film under ultraviolet visible region.So they were proper to meet the requirements of the semiconductor optical absorption layer when the CZTSe films were applied to the photoelectric transformation.At the same time,there were not scattering from the Raman and back to inspire from photoluminescence.It was found that they were favarable to absorbing solar light from impure compositions existed in the CZTSe films from ultraviolet visible region extended to the infrared region.The band gap for the CZTSe films prepared from the inorganic group materials was 1.48 e V,which it is proper to meet the requirements of the semiconductor optical absorption layer when the CZTSe films were applied to the photoelect ric transformation.And it’s worthy mentioning that it was suitable for light-absorbing material in wider spectral range.Subsequently,Copper(II)acetate,zinc acetate,tin(II)chloride and zinc sulfide from the small organic molecules were the sources.Low-cost CZTS films were prepared by using a mild,non-vacuum,sol-gel procedure method under non-toxic sulfide conditions.The preparation process was successful based on realization of the non-toxic vulcanization and low cost of CZTS film preparation.The CZTS films have smooth surface morphology and dense crystal particles.Further,the optical properties of the film properties were analyzed.In the range of visible light 400-1100 nm,the transmittance of the CZTS films is steady and the band gap is 2.32 e V by calculating and proposed cooperation figures,which is so higher than the ideal band gap range of solar energy absorption materials.And the deexcitation and Raman spectrum were not excited in the CZTS films.Because of impure composition s existed in the CZTS films,there were the absorption properties at the near infrared spectroscopy.It was demonstrated that it was beneficial to absorb sun light.At the same time,the impure compositions did not scatter and perform photoluminescence according to the experiment results.Based on the above findings,the films were showed to absorb light in a wider range of spectra in the range of infrared light regions of 2.5-15 μm.It demonstrates that the CZTS films are considered to the promising new solar energy absorption material.Through the proper doping of calcium ions,the band gap width of the organic CZTS film is reduced from 2.32 e V to the optimum value 1.55 e V which is suitable for photoelectric transformation.Next,Copper(II)chloride dihydrate,zinc chloride,tin(IV)chloride pentahydrate,zinc sulfide for the inorganic source material of low molecular weight reagent substances.CZTS films were prepared by using a mild,non-vacuum,sol-gel procedure method.Further,the optical properties of the film properties were analyzed.The preparation process was also successful based on realization of the non-toxic vulcanization and low cost of CZTS film preparation.The film is composed of uniform and ordered dense sphere-like particles,which the observed particles were agglomerated in closely packed clusters to create dense,highly compact,and uniform films.Thus,it is favorable to absorbing light as a porous film with three-dimensional network structure.The zinc-rich CZTS film owned the crystallite size with Cu2 Zn Sn S4.When the thickness of the CZTS films lie in 5-16 μm,the band gaps for the CZTS films prepared from the inorganic materials lie in 1.51 to 1.54 e V,which are matched in the band gap range of solar energy absorption(1.20 to 1.60 e V).Specifically however,the band gap for the CZTS films prepared from the inorganic materials lies in 1.45 e V,which is well matched in the optimal band gap range of solar energy absorption(1.45 to 1.50 e V).So the band gap width is appropriate for the application of photoelectric light absorption material from the inorganic-based copper zinc tin sulfur film by mild sol-gel process.However,they showed light absorption in a wider range of spectral ranges.Thu s,it is predictable to be applied in a wider range of light absorption in photovoltaic technology from ultraviolet visible spectral region extended to the infrared region.In this disseration,it is a successful method for the preparation of the absorbed CZTSe and CZTS films by using a mild,non-vacuum,sol-gel procedure.The method is proved to be in universal by many reactants from inorganic and organic reactants.In this processings to prepare the films,the small organic and inorganic substances as reactants are low-cost and without toxicity.Because of the simplification of procedures,CZTSe and CZTS films are directed to be prepared successfully and the films are considered to the potential promising new solar energy absorption materials.Some parameters such as Raman spectrum,fluorescence spectra,infrared spectrogram,photoluminescence spectrum are all to characterize the soalr absorption of the CZTSe and CZTS films besides of band gap width and light absorption coefficients.It can provide valuable reference to characterize the absorption from the solar in a wider spectrum.And the obtained CZTSe and CZTS films have light absorption in both the visible and the wider spectral range.In addition to the application of photoelectric convers ion,CZTSe and CZTS films have potential applications in absorbed sunlight situations especially in printing coating.更多还原