We present a high-throughput (combinatorial) method to screen thin ceramic films as Li-ion conductors by mapping an optical effect of Li-ion conduction. The method, while qualitative, is fast and simple to implement, provides a planar (XY) map of Li-ion conductivity through different parts of the film. The effect, FTO darkening, is an optoelectrochemical one that relies on darkening of the FTO (F-doped tin oxide) substrate, onto which the investigated film is deposited. The rate of color change of the FTO reflects the rate of Li-ion migration through the film. The method is validated by testing two model systems, a Li-La-S-O film with uniform composition and varying thickness, and a Li-La-P-O film with varying thickness and lateral composition. The darkening rate, obtained from optical transmission, correlates linearly with inverse film thickness. The darkening rate map can be compared with a resistance map obtained by impedance measurements, showing that only Li conduction is measured. We discuss the conditions required to distinguish between areas with pure ion conductivity and those with mixed conductivity, the reversibility of the darkening effect and artifacts.

中文翻译：

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FTO变暗率作为一种高通量的定性方法，用于筛选薄固体电解质中的锂离子传导。

我们提出了一种高通量（组合）方法，通过映射锂离子传导的光学效应来筛选陶瓷薄膜作为锂离子导体。该方法虽然定性，但快速且易于实施，通过薄膜的不同部分提供了锂离子电导率的平面（XY）图。FTO变暗效应是一种光电化学效应，它依赖于FTO（掺F的氧化锡）基板的变暗，在该基板上沉积了所研究的薄膜。FTO的颜色变化速率反映了锂离子穿过薄膜的迁移速率。通过测试两个模型系统验证了该方法的有效性，这两个模型系统分别是具有均匀成分和厚度变化的Li-La-SO膜，以及具有不同厚度和横向成分的Li-La-PO膜。由光透射获得的变暗速率与反膜厚度线性相关。可以将变暗速率图与通过阻抗测量获得的电阻图进行比较，这表明仅测量了Li传导。我们讨论了区分纯离子电导率区域和混合离子电导率区域，变暗效应的可逆性和伪影所需的条件。