Influence of film formation kinetics on the dispersion of colloidal quantum dots in organic small molecule matrices

Abstract

Improving the dispersion of colloidal quantum dots (QDs) within organic semiconductor (OSC) matrices remains critical for advancing hybrid nanocomposite optoelectronic technologies. This study investigates how film-deposition kinetics influence the morphology of TIPS-tetracene (TIPS-Tc):PbS QD blends, comparing spin-coating and blade coating for QDs ligated with either native oleic acid (OA) or a matched carboxylic acid functionalised tetracene analogue (TET-CA). Films spun-cast at low spin speeds form highly crystalline TIPS-Tc domains with highly aggregated QDs. Increased spin speed induces a deeper solvent quench, driving rapid TIPS-Tc nucleation while kinetically arresting QD diffusion, which improves QD dispersion within the crystalline matrix. TIPS-Tc:PbS-OA blends typically exhibit poor QD dispersibility due to poor matching between the OA ligands and the TIPS-Tc matrix. This work demonstrates that through employing high spin speeds QD dispersibilities may be significantly enhanced, even for PbS-OA, a significant step demonstrating that QD-OSC surface chemistries may not have to be fully matched to attain desired, well-dispersed morphologies. In contrast, blade-coating proceeds under slower solvent removal, resulting in weakly crystalline TIPS-Tc and extensive QD aggregation due to extended diffusion and delayed nucleation. These findings reveal the critical role of processing kinetics in directing OSC-QD self-assembly, essential for the optimisation of nanocomposite morphologies for next-generation optoelectronic devices.