Anisotropic conjugated polymer chain conformation tailors the energy migration in nanofibers

TL;DR

This paper demonstrates how controlling the anisotropic conformation of conjugated polymer chains in nanofibers enhances energy transfer and emission properties, advancing optoelectronic device performance.

Contribution

It introduces a method to tailor molecular order in conjugated polymer fibers, significantly improving their optical emission through controlled chain alignment.

Findings

Enhanced emission quantum yield in tailored fibers

Excitation directed along fiber axis within picoseconds

Aligned chromophores lead to improved optical properties

Abstract

Conjugated polymers are complex multi-chromophore systems, with emission properties strongly dependent on the electronic energy transfer through active sub-units. Although the packing of the conjugated chains in the solid state is known to be a key factor to tailor the electronic energy transfer and the resulting optical properties, most of the current solution-based processing methods do not allow for effectively controlling the molecular order, thus making the full unveiling of energy transfer mechanisms very complex. Here we report on conjugated polymer fibers with tailored internal molecular order, leading to a significant enhancement of the emission quantum yield. Steady state and femtosecond time-resolved polarized spectroscopies evidence that excitation is directed toward those chromophores oriented along the fiber axis, on a typical timescale of picoseconds. These aligned and more extended chromophores, resulting from the high stretching rate and electric field applied during the fiber spinning process, lead to improved emission properties. Conjugated polymer fibers are relevant to develop optoelectronic plastic devices with enhanced and anisotropic properties.