Fig. 5: Capping-layer surface chemistry characterization of optimum capping layer (PTEAI).
From: How machine learning can help select capping layers to suppress perovskite degradation

Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) with ZnSe crystal of bare (a, c) and PTEAI-capped MAPbI3 (b, d). e The O 1s spectra obtained from x-ray photoelectron spectroscopy (XPS) of bare and PTEAI-capped MAPbI3, and f their corresponding atomic percentages. The purple circle and the green diamond represent the atomic percentages of O 1s for bare and PTEAI-capped MAPbI3 film, respectively.