Probing the chemistry of perovskite systems by XPS and GD-OES depth-profiling: Potentials and limitations

The capabilities of XPS and GD-OES profiling have been evaluated on a half-cell constituted of glass / FTO / c-TiO
2
/ m-TiO
2
/ triple cation halide perovskites (Cs
0.05
(MA
0.14
, FA
0.86
)
0.95
Pb (I
0.84
, Br
0.16
)
3
), focusing on metrological aspects. The validity of the chemical information measured by those destructive techniques is accurately studied, considering the possible modification inherent to the techniques themselves: X-Ray illumination, UHV, bombardment by Ar ions (mono or polyatomic). XPS and GD-OES have shown similar trends for the composition profiles. But the conditions employed for XPS profiling lead to a systematic reduction of lead, which could not be avoided as well as the organic part degradation and iodine loss. Nevertheless, differences of XPS depth profiles obtained using either Ar
⁺
or ${\text{Ar}}_{\text{n}}^ +$ have raised the question of the bombardment effect on the perovskite surface, influencing the reliability of the collected chemical information. The chemical and morphological study of the XPS and GD-OES crater is presented. The possibility to combine those two techniques for an advanced chemical characterization of perovskite stacks is discussed.