The impact of processing on the optical absorption onset of CdTe thin-films and solar cells
The impact of processing on the optical absorption onset of CdTe thin-films and solar cells
复制标题
DOI：
10.1063/5.0033415
复制
发表时间：
2021-04-28
影响因子：
3.2
通讯作者：
Collins, R. W.
中科院分区：
文献类型：
--
作者：
Andrews, J. J.;Beaudoin, M.;Collins, R. W.
我们重点研究了制备碲化镉(CdTe)太阳能电池常用的两个工艺步骤，即氯化镉处理和随后的溴/甲醇湿法刻蚀工艺，它们如何影响多晶CdTe薄膜的结构和光学性质。特别是，结合光热偏转光谱和椭圆偏振光谱的实验结果，我们确定了射频溅射(RFS)和近空间升华(CSS)CdTe样品的光吸收系数α(E)在1.1-2.0 eV的光子能量范围内的光谱依赖性。还考察了这些工艺步骤对掠入射X射线衍射图整形的影响。我们通过解释两个氯化镉处理的基于镉的太阳能电池的外部量子效率的光谱相关性，将分析扩展到器件。除了吸收体，一种是RFS法，另一种是CS法，电池的制备方法是相似的。通过使用我们对薄膜CdTe光学功能的研究结果和太阳电池多层结构的模型，我们模拟了所得到的外量子效率谱。通过与相应的太阳电池实验结果的对比，我们对两种类型的CdTe吸收体内发生的载流子捕获和复合过程进行了深入的了解。
We critically examine how two processing steps commonly applied in the preparation of cadmium telluride (CdTe)-based solar cells, i.e., the cadmium chloride treatment and the subsequent stepwise bromine/methanol wet etching process, impact the structural and optical properties of polycrystalline CdTe thin-films. In particular, drawing upon a conjuncture of photothermal deflection spectroscopy and spectroscopic ellipsometry experimental results, we determine the spectral dependence of the optical absorption coefficient, alpha (E), over the photon energy range from 1.1 to 2.0eV for samples of rf sputtered (RFS) and close space sublimation (CSS) CdTe. The impact of these processing steps on shaping the grazing incidence x-ray diffraction pattern is also examined. We extend the analysis to devices through interpretation of the spectral dependence of the external quantum efficiency associated with two cadmium chloride treated CdTe-based solar cells. The cells are comparably prepared with the exception of the absorber, one by RFS and the other by CSS. Through the use of our results for the thin-film CdTe optical functions and a model for the solar cell multilayer structure, we simulate the resultant external quantum efficiency spectrum. Through a critical contrast with the corresponding solar cell acquired experimental results, we glean insights into the carrier trapping and recombination processes that occur within the two types of CdTe absorbers.