In situ Near‐Ambient Pressure X‐ray Photoelectron Spectroscopy Reveals the Influence of Photon Flux and Water on the Stability of Halide Perovskite

Abstract

For several years, scientists have been trying to understand the mechanisms that reduce the long‐term stability of perovskite solar cells. In this work, we examined the effect of water and photon flux on the stability of CH3NH3PbI3 perovskite films and solar cells using in situ near‐ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS), field emission scanning electron microscopy (FESEM), and current density–voltage (J–V) characterization. The used amount of water vapor (up to 1 mbar) had a negligible impact on the perovskite film. The higher the photon flux, the more prominent were the changes in the NAP‐XPS and FESEM data; also, a faster decline in power conversion efficiency (PCE) and a more substantial hysteresis in the J‐V characteristics were observed. Based on our results, it can be concluded that the PCE decrease originates from the creation of Frenkel pair defects in the perovskite film under illumination. The stronger the illumination, the higher the number of Frenkel defects, leading to a faster PCE decline and more substantial hysteresis in the J‐V sweeps.

Top‐Down Approach to Study Chemical and Electronic Properties of Perovskite Solar Cells: Sputtered Depth Profiling Versus Tapered Cross‐Sectional Photoelectron Spectroscopies

“…However, in our previous studies, we found that the perovskite is stable under X‐ray exposer under the vacuum unless any external factor such as heat, moisture, or visible light is provided to the system. [ 19,23,30–34 ]…”

Disentangling X‐Ray and Sunlight Irradiation Effects Under a Controllable Atmosphere in Metal Halide Perovskites

“…Besides, halide segregation depends on stoichiometry, crystallinity, defects, atmosphere, and temperature. [12,[18][19][20][21][22][23][24][25][26] A consequence of the phase segregation is the observed emission redshift and the increase in the relative PL quantum yield-photobrightening-as the iodide-rich domains serve as sinks for the photogenerated carriers. [27] Despite several reports in the literature that have introduced approaches to prevent halide segregation and proposed mechanisms, the diversity of parameters that influence this phenomenon and its reversibility makes its study challenging.…”

Surface stability of ionic-liquid-passivated mixed-cation perovskite probed within situphotoelectron spectroscopy

“…39,40 During NAP-XPS measurements, a peak at ∼536 eV BE associated with gas phase water vapour was observed. 41 The O 1s core level signal showed an increase in intensity after the NAP-XPS measurements (Fig. S4 and Table S2†), suggesting further incorporation of water after exposure.…”