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-TiO2 / m-TiO2 / 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 Ar-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.

Automated summary

XPS and GD-OES techniques were evaluated for chemical characterization of perovskite stacks, with XPS profiling leading to a reduction of lead and degradation of organic part. Differences in XPS depth profiles with different Ar ion types raised concerns about the bombardment effect on the perovskite surface, affecting the reliability of the chemical information collected. The possibility of combining XPS and GD-OES for advanced chemical characterization of perovskite stacks was discussed.