Fe掺杂CuGaS2中间带薄膜材料的制备及光电特性

The micro- and nano- grain precursor paste is synthesized by mechanically milling or solvothermal decomposition. Afterwards, CuGaS2:Fe intermediate band thin films will be prepared by sequentially compacting, sintering and surface treatment of this precursor paste. The chemical ingredient, phase structure, grain size, morphology, uniformity and densification of the samples in the four technical processes will be analyzed and monitored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS), scanning electron microscopy (SEM), Atomic Force Microscope (AFM), Raman spectra, and so on. By adjusting Fe composition and the stoichiometry of CuGaS2 host material, whether there is an impurity intermediate band forming in a CuGaS2:Fe film will be verified by many test methods such as the optical and electrical measurements, photovoltage spectra and photoconductivity spectra, and so on. Electron states and impurity states of these films will be theoretically calculated to determinate the effect of Fe impurity and electron-phonon interaction in the process of optical absorption and electronic transport. The doping mechanism and the conditions for impoving the photoelectric performance of CuGaS2:Fe intermediate band thin films will be studied experimentally and theoretically for their effective application in window layers or absorbing layers of solar cells. It is expected that scientific evidences can be provided for the development of related thin film cells via this project.

采用机械球磨或溶剂热分解合成微纳米颗粒前驱体料浆，经过压制、烧结和表面处理制备CuGaS2:Fe中间带薄膜。采用XRD、XPS、EDS、SEM、AFM以及Raman谱等测试方法分析监测样品在四个工艺环节的化学成分、相结构、晶粒尺寸、表面截面形貌以及薄膜均匀性和致密度等性质。调节Fe组分和CuGaS2基底材料化学计量比，通过光学测试和电学测试以及光电压谱和光电导谱等多种测试方法检验CuGaS2:Fe薄膜中是否形成杂质中间带。理论计算薄膜的电子态和杂质态，研究Fe杂质和电声子相互作用在光学吸收和电子输运过程中的作用。从实验和理论上探讨CuGaS2:Fe中间带薄膜的掺杂机制和光电性能优化条件，以便其有效应用于太阳电池的窗口层或吸收层，为研制相关薄膜太阳电池提供科学依据。

采用粉末冶金工艺，即：控制化学计量比，配料Cu2S、Ga2S3、Fe2S3、In2S3、Ce2S3、TiS2、ZnS等二元化合物粉末，将配比合适的混料加入一定比例的乙醇进行球磨，然后采用旋涂法将球磨好的浆料涂覆在玻璃衬底上，调节不同的退火温度在Ar或N2氛围中进行烧结，分别制备CuGaS2薄膜、CuGaS2:Fe薄膜、CuGaS2:Ti中间带薄膜、CuGaS2:Ti：Zn中间带薄膜、CuInS2薄膜和CuInS2:Ce中间带薄膜。采用XRD、XPS、EDS、SEM等表征手段测试分析样品的化学成分、相结构、晶粒尺寸、表面截面形貌以及薄膜均匀性和致密度等性质。实验结果表明，采用粉末冶金法制备的上述薄膜都为多晶薄膜，主要呈黄铜矿结构，但含有不少二元杂相。薄膜的晶化效果跟退火温度有关，选择500至600℃退火温度，结晶情况最佳。此外，薄膜的晶粒尺寸大，表面致密且比较平整、均匀、无明显空洞。光学测试为UV-vis紫外分光光度计测试薄膜样品的吸收峰并推算其光学带隙，我们测得，CuGaS2的光学带隙为2.46eV，CuInS2的光学带隙为1.45eV，适合作为中间带材料的基底材料。Ti掺杂的CuGaS2和Ce掺杂的CuInS2薄膜的吸收谱显示，在主吸收峰侧有子峰出现，经初步证实能形成中间带，而Fe掺杂的CuGaS2我们并未观察确认中间带。同时，对于中间带在基底材料禁带宽度位置的调节，我们尝试了Zn和Ti共掺，通过调节Zn的掺杂比例，可以调节中间带的位置，以利于其在薄膜电池中的利用。我们判断Fe掺杂的CuGaS2未能形成中间带的原因主要是Fe元素的二元和三元杂相居多。为此，围绕CuGaS2基底中间带材料的制备，我们进一步摸索了梯度功率调节磁控溅射工艺和在普通玻璃衬底上利用磁控溅射法沉积ITO/Ag/ITO薄膜用于衬底优化，以期通过上述两种方法能进一步制备没有杂相且可实际应用的CuGaS2基底中间带材料。