Electron holography is employed to study variations of the electrostatic crystal potential in Cu(In,Ga)Se2 (CIGS) thin-film solar cells at different length scales: Long-range potential variations across the layer structure of the solar cell as well as inhomogeneities within the layers are analyzed by off-axis holography. In-line holography is applied to examine the local potential variation across a CIGS grain boundary. The phase reconstruction from a focal series is performed by a modified transport of intensity equation (TIE) which is optimized to reduce common artifacts. For comparison, three different microscopes of different optical configurations were used for in-line holography. Based on the results, the impact of the used microscope as well as further acquisition parameters on the in-line holography measurement is assessed. The measured potential variations are discussed considering the effect of different possible sources that may cause potential fluctuations. It is found that most of the variations are best explained by mean inner potential fluctuations rather than by inhomogeneities of the electronic properties. Finally, the present resolution limit of both methods is discussed regarding the feasibility of future electronic characterization of CIGS by holography.

中文翻译：

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评估用于测量Cu（In，Ga）Se ₂薄膜太阳能电池中电位变化的离轴和在线电子全息术

电子全息技术用于研究不同长度尺度的Cu（In，Ga）Se2（CIGS）薄膜太阳能电池中静电晶体电势的变化：整个太阳能电池层结构上的远距离电势变化以及不均匀性通过离轴全息术分析层内的层。在线全息技术用于检查整个CIGS晶界的局部电势变化。通过改进的强度方程（TIE）传输，可以对焦点序列进行相位重建，该方程经过优化可以减少常见的伪像。为了进行比较，将三个具有不同光学配置的不同显微镜用于在线全息照相。根据结果​​，评估所用显微镜以及在线成像测量中其他采集参数的影响。考虑到可能引起电位波动的不同可能来源的影响，讨论了测得的电位变化。发现大多数变化最好用平均内部电势波动来解释，而不是通过电子特性的不均匀性来解释。最后，讨论了通过全息技术对CIGS进行未来电子表征的可行性，讨论了这两种方法的当前分辨率极限。