Optical heterostructure in a two-dimensional organic crystal

TL;DR

The paper describes a new organic crystal structure that creates optical heterostructures with enhanced fluorescence in a single material.

Contribution

The novel contribution is the creation of an intrinsic optical heterostructure in a single-component organic nanosheet.

Findings

An organic nanosheet exhibits enhanced fluorescence in its inner zone due to a localized solid-state transition.

The transition forms an out-of-plane twin structure, increasing radiative recombination efficiency.

The phenomenon arises from competitive interactions between molecules and the substrate.

Abstract

Optical heterostructures, which feature spatially heterogeneous optical properties at the subwavelength scale, represent a key frontier for next-generation integrated photonics and optoelectronics. While typically realized by joining dissimilar materials, achieving such heterogeneity in single-component systems has remained a fundamental challenge. Here, we report an intrinsic optical heterostructure in a uniform organic nanosheet, manifesting as strongly enhanced fluorescence in the inner zone compared to the outer zone. We demonstrate that this emission heterogeneity stems from a spatially localized solid-state transition in the central top layer, which transforms the initial single crystal into an out-of-plane twin structure and significantly enhances the radiative recombination efficiency. This transition is driven by the competitive interplay between molecule-substrate and intermolecular interactions, as corroborated by multiscale structural, optical, and theoretical analyses. Our findings not only establish a platform for realizing optical heterostructures in organic materials but also open avenues for exploring structural-dynamics-governed photonic phenomena, offering broad implications for future materials design and micro-optical applications.

Optical heterostructures have potential in integrated photonics and optoelectronics but are challenging to prepare in single-component systems. Here, the authors report an intrinsic optical heterostructure in an organic nanosheet, with enhanced fluorescence in an inner zone.

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