Supramolecular self-assembly as a tool to preserve electronic purity of perylene diimide chromophores

TL;DR

This study demonstrates that supramolecular self-assembly of a pseudo-cube structure with modified perylene diimides preserves their electronic purity and enhances optoelectronic properties by preventing aggregation and quenching effects.

Contribution

It introduces a novel supramolecular pseudo-cube that maintains the electronic integrity of PDI chromophores, enabling improved optoelectronic performance in organic semiconductors.

Findings

Suppressed aggregation and fluorescence quenching in the cage structure

Observation of delayed fluorescence from multimer states

Geometric control of electronic properties in supramolecular systems

Abstract

Small molecule organic semiconductors hold great promise for efficient, printable, and flexible optoelectronic applications like solar cells and displays. However, strong excited-state quenching due to uncontrolled aggregation currently limits their performance and employability in devices. Here, we report on the self-assembly of a supramolecular pseudo-cube formed from six modified tetradentate perylene diimides (PDIs). The rigid, shape-persistent cage sets the distance and orientation of the PDI chromophores and suppresses intramolecular rotations and vibrations, leading to non-aggregated, monomer-like electronic properties in solution as well as in the solid state, in contrast to the fast fluorescence quenching in the free ligand. The stabilized excited state and electronic purity of the cage enable the observation of delayed fluorescence due to a bright excited multimer state, which acts as an excited state reservoir, due to a rare case of benign inter-chromophore interactions in the cage. Our results suggest that not only the photophysical properties of the subcomponents but the geometric structure is crucial for the overall optoelectronic properties of supramolecular systems. We show that self-assembly provides a powerful tool for retaining and controlling the electronic properties of well-studied chromophores, providing a route to bring molecular electronics applications in reach.