First principles modeling of exciton-polaritons in polydiacetylene chains

TL;DR

This paper develops a first principles modeling approach to quantify exciton-polaritons in organic materials, specifically polydiacetylene chains, revealing the importance of polymer length and vibrational coupling for strong light-matter interactions.

Contribution

It introduces a novel first principles method to analyze exciton-polaritons in organic polymers, enabling molecular design for optoelectronic applications.

Findings

Large conjugation length enhances exciton-photon coupling.

Vibrational coupling significantly affects light-matter interaction.

Experimental validation confirms the model's predictions.

Abstract

Exciton-polaritons in organic materials are hybrid states that result from the strong interaction of photons and the bound excitons that these materials host. Organic polaritons hold great interest for optoelectronic applications, however progress towards this end has been impeded by the lack of a first principles approach that quantifies light-matter interactions in these systems, and which would allow the formulation of molecular design rules. Here we develop such a first principles approach, quantifying light-matter interactions. We exemplify our approach by studying variants of the conjugated polymer polydiacetylene, and we show that a large polymer conjugation length is critical towards strong exciton-photon coupling, hence underlying the importance of pure structures without static disorder. By comparing to our experimental reflectivity measurements, we show that the coupling of excitons to vibrations, manifested by phonon side bands in the absorption, has a strong impact on the magnitude of light-matter coupling over a range of frequencies. Our approach opens the way towards a deeper understanding of polaritons in organic materials, and we highlight that a quantitatively accurate calculation of the exciton-photon interaction would require accounting for all sources of disorder self-consistently.