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

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.