Improving Nanoparticle Dispersion in Organic-Inorganic Nanocomposite Blends via Low-Temperature Processing

Nanocomposite films formed from blends of organic semiconductors and inorganic colloidal quantum dots are promising systems for low cost, high efficiency solar energy harvesting technologies.^[1,2] Optimum device performance requires a precise nanoscale film morphology consisting of quantum dots well dispersed throughout the organic semiconductor matrix. However, this poses a significant challenge due to the strong tendency of the inorganic and organic components to aggregate and phase-separate. Understanding and controlling the self-assembly of nanocomposite films is therefore crucial to optimizing energy harvesting performance. Here, a low-temperature thermal processing approach is presented to improve quantum dot dispersion in organic matrices, yielding solution-processed films with reduced aggregation and phase-separation. Self-assembly and film formation are characterized in-situ with grazing incidence X-ray scattering (GIXS) during high throughput film coating and post-deposition thermal processing. The approach is applied to a promising energy harvesting system based on a soluble diphenylhexatriene singlet fission host blended with surface functionalized lead sulfide quantum dots. The work explores how matching quantum dot surface chemistry to different functional groups of the organic semiconductor matrix impacts the self-assembly and thermal response of solution-processed nanocomposite films. Importantly, structural design rules and processing routes are provided to overcome the challenges in blending organic semiconductors with quantum dots for targeted morphologies. The proposed methodologies are compatible with large-scale deposition manufacturing techniques that are crucial to driving the wider adoption of emerging energy harvesting strategies.

[1] A. Rao, R. H. Friend, Nat. Rev. Mater. 2017, 2, 17063.
[2] V. Gray et al., J. Am. Chem. Soc. 2024, 146, 7763.