FTO Darkening Rate as a Qualitative, High-Throughput Mapping Method for Screening Li-Ionic Conduction in Thin Solid Electrolytes Shay Tirosh Niv Aloni Simcha Meir Arie Zaban David Cahen Diana Golodnitsky 10.1021/acscombsci.9b00099.s001 https://acs.figshare.com/articles/media/FTO_Darkening_Rate_as_a_Qualitative_High-Throughput_Mapping_Method_for_Screening_Li-Ionic_Conduction_in_Thin_Solid_Electrolytes/11310140 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, <i>FTO darkening</i>, 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. 2019-12-03 14:03:45 FTO Darkening Rate Screening Li-Ionic Conduction resistance map color change High-Throughput Mapping Method model systems rate map Li conduction impedance measurements Li-ion migration method Li-ion conduction film thickness XY ion conductivity Li-ion conductors Li-ion conductivity F-doped tin oxide uniform composition