Jem 2100f tem stem

The composition and orientation of (PEA)₂(MA)_n−1Pb_nI_3n+1 perovskite layer was confirmed by XRD (Rigaku SmartLab). The PL spectra of perovskite films were acquired by photoluminescence spectrometer (Edinburgh: FLS920) with excitation wavelength of 488 nm. The absorption spectra of perovskite films were recorded by Perkin Elmer UV–vis–NIR spectrometer. The FIB milling process and the cross‐sectional FIB‐TEM images were conducted using JEOL JIB‐4501F and JEOL JEM‐2100F TEM/STEM, respectively.

Transmission electron microscopy (TEM) images were obtained using a JEM-2100F TEM/STEM (JEOL, Japan) operated at an acceleration electron beam voltage of 200 kV. Field-emission scanning electron microscopy (FE-SEM) images and energy-dispersive X-ray (EDS) analysis were performed using an S4700 (Hitachi High-Tech, Japan). X-ray diffraction (XRD) patterns were recorded using a SmartLab diffractometer (Rigaku, Japan) with Cu Kα radiation (λ = 1.5418 Å). A Si non-reflective plate was used as the substrate. UV–visible (UV–Vis) diffuse reflectance spectra were recorded using a spectrophotometer (V-670, JASCO, Japan) equipped with an integration sphere unit. Optical absorption spectra were obtained using the Kubelka–Munk function^{44 (link)} calculated from raw reflection data, where a white BaSO₄ plate was used as the reflectance standard. Electron spin resonance (ESR) spectra were recorded using an in situ ESR system under light irradiation (EMX Nano, Bruker). For ESR measurements, the photocatalyst powder was placed into a quartz tube filled with nitrogen gas at 90 K with a microwave frequency (X-band) of 9.629 GHz to 9.633 GHz.

TEM and STEM of the cross-sectional samples were performed using JEOL JEM-2100F TEM/STEM (Tokyo, Japan) operated at 200 kV. EELS mapping was carried out under 200 kV accelerating voltage with a 13 mrad convergence angle for the optimal probe condition. Energy dispersion of 0.7 eV per channel and 21 mrad collection angle were set up for EELS. High-angle annular dark-field STEM images were acquired with an 89 mrad inner angle simultaneously. The N and S intensity maps were extracted from the EELS mapping by integrating across the energy windows of 401–409 (K edge) and 162–173 (L_2,3 edge) eV, respectively.