Optical Microscopy Approach to Correlate Structural and Energy Conversion Properties of Nanoscale Materials

At a Glance

Researchers at Colorado State University have developed an approach to combine functional data with structural data for a wide range of materials. The approach overlays structural (e.g., electron, scanning probe, or optical microscopy images) and functional images (e.g., PL, Raman, Photocurrent images), which is particularly useful for ultrathin nanosystems (such as 2D transition metal dichalcogenides (MoS2) and perovskite  photovoltaics). The method incorporates novel software as well as hardware modifications to quantitatively and seamlessly screen material performance in a single step.

Background

Monolayer (Transition metal dichalcogenide) TMDs represent the ultimate miniaturization limit for efficient ultrathin and ultralight photovoltaics with continued interest in application toward space power systems, internet-of-things devices, as well as portable and flexible electronics. For large area application, defected and heterogeneity in these systems play an essential role in determination of overall device performance. And while many industries and research domains measure functional signals (Ex: light emission, photo-induced current) using focused laser beams, no such technique exists to overlay those images with topographical data seamlessly and quantitatively.

Overview

Novel algorithms along with hardware modifications to the microscopic / spectroscopic apparatus allows for the collection and processing of reflected laser signal.

Figure 1 Structural overlay procedure using TMD features below depicts:

Figure 1. A. Bright field optical transmission image of the TMD sample in an iodide electrolyte; B. Photocurrent map; and C. laser reflection map of the same region in (A). Control point pairs labeled 1, 2, and 3 in (A) and (C) represent the centroid position of the same structural features in two different images. D. Quantitative overlay of the optical transmission image onto the photocurrent map (i.e., the color-coded pixels). Red pixels = monolayer thickness, blue pixels = bilayer thickness, and green pixels = multi-layer thickness. The thick symbols represent edge pixels. The interior pixels of multi-layer material were not color-coded for clarity.

Benefits

  • Fast, efficient screening of materials
  • Simple modification to existing designs
  • Allows for easy to see structure-function relationships
Last Updated: October 2022