Facet-Dependent Photoelectrochemistry on Single Crystal Organic–Inorganic Halide Perovskite Electrodes

Abstract

Organometallic halide perovskites have garnered significant attention in various fields of material science, particularly solar energy conversion, due to their desirable optoelectronic properties and compatibility with scalable fabrication techniques. It is often unclear, however, how carrier generation and transport within complex polycrystalline films are influenced by variations in local structure. Elucidating how distinct structural motifs within these heterogeneous systems affect behavior could help guide the continued improvement of perovskite-based solar cells. Here, we present studies applying scanning electron microscopy (SECCM) to map solar energy harvesting within well-defined model systems of organometallic halide perovskites. Methylammonium lead bromide (MAPbBr 3 ) single crystals were prepared via a low-temperature solution-based route, and their photoelectrochemical properties were mapped via SECCM using p-benzoquinone (BQ) in dichloromethane as a redox mediator. Correlated SECCM mapping and electron microscopy studies enabled facet-to-facet variations in photoelectrochemical performance to be revealed and carrier transport lengths to be evaluated. The photoelectrochemical behavior observed within individual single crystals was quite heterogeneous, attributable to local variations in crystal structure/ orientations, intrafacet junctions, and the presence of other structural defects. These observations underscore the significance of controlling the microstructure of single perovskite crystals, presenting a promising avenue for further enhancement of perovskitebased solar cells.

Recent Developments in Single-Entity Electrochemistry

“…A trend in SEE with SECCM is the study of single nanocrystals with controlled size, shape, facet, and surface area. ,− Jeong et al employed SECCM to resolve activity for electrochemical CO 2 reduction (eCO 2 RR) at faceted single-crystalline Au nanocrystals . Three differently faceted nanocrystals were designed to have the same surface area.…”

Five years of scanning electrochemical cell microscopy (SECCM): new insights and innovations

“…To investigate this, Hill et al employed SECCM under uniform illumination to reveal facet-to-facet variations in the PEC performance of a methylammonium lead bromide (MAPbBr 3 ) perovskite single crystal. 99 In highly faceted systems, poor local performance was identified at boundaries between adjacent facets and structural defects, whereas for flat crystals the PEC behaviour was more homogeneous, albeit with increased photocurrents observed near the crystal edges. The local PEC analysis was supplemented by CG-TC SECCM to characterise the diffusion length of photogenerated carriers, resulting in a comprehensive nanoscale investigation of the most important solar harvesting properties for polycrystalline materials.…”