Research on Thickness Measurement of Perovskite Coatings Based on Energy-Dispersive X-ray Intensity Ratio

The simulated structure included a glass substrate, SnO₂ layer, and FAPbI₃ coating (270–900 nm). X-ray fluorescence spectra were simulated to obtain net peak intensities of elements such as I, Ca, Sn, and Si. Four types of X-ray intensity ratios were calculated: I-Lβ₁/I-Lα, I-Lα/Ca-Kα, Ca-Kα/Si-Kα, and Sn-Lα/Si-Kα.

These ratios were fitted against coating thickness to establish calibration curves. For validation, EDXRF experiments were conducted on perovskite samples with the same layer structure using a Mo-target X-ray tube and a silicon drift detector. Experimental intensity ratios were compared with simulated values, and coating thicknesses were inversely predicted using the calibration curves.

The method's accuracy was evaluated by calculating relative errors between simulated and experimental ratios, as well as between predicted and actual thicknesses.[Conclusions] In the experimental verification, the relative error between the simulated and experimental data of the I-Lβ1/I-Lα element group was less than 3.5%, and the relative error between the inversion thickness and the actual thickness was less than 15%.

The effect was the best among all element groups, confirming the applicability of the proposed thickness measurement method in the thickness measurement of multi-layer complex coatings.