Scanning x-ray excited optical luminescence of heterogeneity in halide perovskite alloys

Abstract

Understanding the optoelectronic properties of optically active materials at the nanoscale often proves challenging due to the diffraction-limited resolution of visible light probes and the dose sensitivity of many optically active materials to high-energy electron probes. In this study, we demonstrate correlative synchrotron-based scanning x-ray excited optical luminescence (XEOL) and x-ray fluorescence (XRF) to simultaneously probe local composition and optoelectronic properties of halide perovskite thin films of interest for photovoltaic and optoelectronic devices. We find that perovskite XEOL stability, emission redshifting, and peak broadening under hard x-ray irradiation correlates with trends seen in photoluminescence measurements under continuous visible light laser irradiation. The XEOL stability is sufficient under the intense x-ray probe irradiation to permit proof-of-concept correlative mapping. Typical synchrotron XRF and nano-diffraction measurements use acquisition times 10–100x shorter than the 5-second acquisition employed for XEOL scans in this study, suggesting that improving luminescence detection should allow correlative XEOL measurements to be performed successfully with minimal material degradation. Analysis of the XEOL emission from the quartz substrate beneath the perovskite reveals its promise for use as a real-time in-situ x-ray dosimeter, which could provide quantitative metrics for future optimization of XEOL data collection for perovskites and other beam-sensitive materials. Overall, the data suggest that XEOL represents a promising route towards improved resolution in the characterization of nanoscale heterogeneities and defects in optically active materials that may be implemented into x-ray nanoprobes to complement existing x-ray modalities.