Nanometric Chemical Analysis of Beam‐Sensitive Materials: A Case Study of STEM‐EDX on Perovskite Solar Cells

Abstract

Quantitative chemical analysis on the nanoscale provides valuable information on materials and devices which can be used to guide further improvements to their performance. In particular, emerging families of technologically relevant composite materials such as organic–inorganic hybrid halide perovskites and metal‐organic frameworks stand to benefit greatly from such characterization. However, these nanocomposites are also vulnerable to damage induced by analytical probes such as electron, X‐ray, or neutron beams. Here the effect of electrons on a model hybrid halide perovskite is investigated, focusing on the acquisition parameters appropriate for energy‐dispersive X‐ray spectroscopy in a scanning transmission electron microscope (STEM‐EDX). The acquisition parameters are systematically varied to examine the relationship between electron dose, data quality, and beam damage. Five metrics are outlined to assess the quality of STEM‐EDX data and severity of beam damage, further validated by dark field STEM imaging. Loss of iodine through vacancy creation is found to be the primary manifestation of electron beam damage in the perovskite specimen, and iodine content is seen to decrease exponentially with electron dose. This work demonstrates data acquisition and analysis strategies that can be used for studying electron beam damage and for achieving reliable quantification for a broad range of beam‐sensitive materials.

Upscaling Inverted Perovskite Solar Cells: Optimization of Laser Scribing for Highly Efficient Mini-Modules

“…The current and voltage settings are 27 pA, 2 kV for imaging and 200 pA, 10 kV for EDX mapping. For cross-sectional TEM imaging, a lamella was prepared using a FEI Helios Nanolab Dualbeam FIB/SEM following a standard procedure [ 27 ]. This lamella was then immediately transferred into a FEI Osiris TEM operated in scanning mode (STEM) at 200 kV.…”

Aerosol Assisted Solvent Treatment: A Universal Method for Performance and Stability Enhancements in Perovskite Solar Cells

“…(color scale corresponds to deviation from stoichiometry of 3), the thin red strips at the perovskite-PCBM interface in the I/Pb maps are due to electron beam-induced iodine migration towards PCBM. [40] g,h) EDX mapping of Pb/N concentration (color scale corresponds to deviation from stoichiometry of 1). Scale bars in all EDX maps correspond to 200 nm.…”

“…b) Magnified view of the (110) diffraction peaks, note these data are normalized for comparison of peak position and full width at half maximum. c,d) Cross-sectional scanning transmission electron microscopy-high angle annular darkfield (STEM-HAADF) images of complete solar cells (scale bars = 200 nm), e,f) Energy dispersive X-ray spectroscopy (EDX) mapping showing the spatial modulation in the I/Pb concentration ratios(color scale corresponds to deviation from stoichiometry of 3), the thin red strips at the perovskite-PCBM interface in the I/Pb maps are due to electron beam-induced iodine migration towards PCBM [40]. g,h) EDX mapping of Pb/N concentration (color scale corresponds to deviation from stoichiometry of 1).…”

Improved Electrical Performance of Perovskite Photovoltaic Mini‐Modules through Controlled PbI2 Formation Using Nanosecond Laser Pulses for P3 Patterning

“…The STEM‐EDX spectrum images were obtained with a Bruker Super‐X silicon drift detector with a solid collection angle of about 0.9 sr. To minimize beam damage, a defocused beam (Δ f = −1 μm) with a beam current of about 130 pA, a dwell time of 30 ms/pixel, and spatial sampling of 10 nm/pixel was used. [ 26 ] The STEM‐EDX data was denoised with principal component analysis and processed in HyperSpy, a Python‐based analysis suite for hyperspectral data. [ 27 ] Spectrally filtered PL microscopy measurements were performed using a commercially available fluorescence lifetime imaging (FLIM) setup (Becker & Hickl, DCS 120) equipped with a 488 nm pulsed ps diode laser (BDS‐SM, Becker & Hickl) and a photosensitive detector module (B&H, HPM‐100).…”