Novel Detection Scheme for Temporal and Spectral X-Ray Optical Analysis: Study of Triple-Cation Perovskites

Abstract

Multimodal x-ray microscopy is key to assessing the property-functionality relationships of semiconductor devices with the utmost sensitivity and spatial resolution. Here, we report on a novel setup—the “Analyzer of X-ray excited Optical Luminescence Offering Temporal and spectraL resolution” (AXOLOTL)—and demonstrate its use by investigating a series of triple-cation mixed-halide perovskite solar cells (PSCs) with varying Cs content. These PSCs exhibit spatially varying performance and are thus ideally probed by multimodal x-ray microscopy to elucidate the origin of the performance variations. Specifically, our nanoscale characterization of the wrinkled perovskite photoabsorber unveils a segregation of I and Br, which is accompanied by a narrowed band gap and an increased charge-carrier lifetime in thick absorber areas. Overall, we demonstrate with this technique the spatial correlation of compositional inhomogeneities, topography, electrical performance, and optical performance, which is of highest interest for identifying loss mechanisms at the nanoscale in high-performance electronic device development, including solar cells.