Designing for Dispersibility: How Crystallinity and Solubilizing Groups Affect Quantum Dot Dispersion in Diphenylhexatriene Matrices

TL;DR

This study shows how the design of organic semiconductor materials affects the dispersion of quantum dots in nanocomposite films for optoelectronic applications.

Contribution

A new design rule for improving quantum dot dispersibility in diphenylhexatriene matrices by tuning solubilizing groups.

Findings

PbS quantum dots with oleic acid ligands are poorly dispersed in DPH derivatives.

Hexanoic acid or DPH-carboxylic acid ligands significantly improve quantum dot dispersibility.

Amorphous DPH derivatives can initially disperse QDs but later cause aggregation upon crystallization.

Abstract

Nanocomposite
films combining organic semiconductors (OSCs) and
colloidal quantum dots (QDs) are promising systems for next-generation
optoelectronic technologies such as singlet-fission photon multiplication
(SF-PM). Here, we show that tuning the solubilizing substituents on
the high-triplet-energy SF-OSC (1E,3E,5E)-1,6-diphenylhexa-1,3,5-triene (DPH) enables
precise control over film morphology and QD dispersibility. Grazing-incidence
X-ray scattering reveals that PbS QDs ligated with oleic acid are
poorly dispersed in all DPH derivatives, whereas hexanoic acid or
DPH-carboxylic acid ligands significantly improve QD dispersibility.
A clear design rule emerges: increasing solubilizing group volume
relative to the DPH core enhances QD dispersibility, enabling well-dispersed
QDs even in highly ordered DPH matrices. An exception arises in a
derivative that forms an amorphous, nonequilibrium morphology that
fully disperses QDs, but later crystallizes, resulting in QD aggregation.
These findings show that OSC:QD nanocomposites require co-optimization
of ligand–OSC chemistry and crystallization kinetics, providing
a framework for designing efficient SF-PM and related technologies.

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