White-light generating molecular materials: correlation between the amorphous/crystalline structure and nonlinear optical properties

TL;DR

This study introduces transmission electron microscopy techniques to analyze the local structure of amorphous and crystalline regions in molecular materials, revealing how nanoscopic arrangements influence their nonlinear optical properties.

Contribution

It provides a novel method to directly correlate local amorphous/crystalline structure with optical properties in molecular materials.

Findings

Nanoscopic structure correlates with optical responses.

Amorphous regions contribute to nonlinear optical properties.

Transmission electron microscopy effectively characterizes local structure.

Abstract

Amorphous materials are integral part of todays technology, they commonly are performant and versatile in integration. Consequently, future applications increasingly aim to harvest the potential of the amorphous state. Establishing its structure-property relationship, however, is inherently challenging using diffraction-based techniques yet is extremely desirable for developing advanced functionalities. In this article, we introduce a set of transmission electron microscopy-based techniques to locally quantify the structure of a material. This unique approach allows to clearly identify the spatial distribution of amorphous and crystalline regions and to quantify atomic arrangements of amorphous regions of a representative model system. We study an ensemble of well-defined, functionalized adamantane-type cluster molecules exhibiting exceptionally promising nonlinear optical properties of unclear origin. The nanoscopic structure for three model compounds ([(PhSn)4S6], [(NpSn)4S6], [(CpSn)4S6]) correlates with their characteristic optical responses. These results highlight the advantageous properties of amorphous molecular materials when understanding the microscopic origin.