Abstract
AbstractControlling the dispersibility of crystalline inorganic quantum dots (QD) within organic‐QD nanocomposite films is critical for a wide range of optoelectronic devices. A promising way to control nanoscale structure in these nanocomposites is via the use of appropriate organic ligands on the QD, which help to compatibilize them with the organic host, both electronically and structurally. Here, using combined small‐angle X‐ray and neutron scattering, the authors demonstrate and quantify the incorporation of such a compatibilizing, electronically active, organic semiconductor ligand species into the native oleic acid ligand envelope of lead sulphide, QDs, and how this ligand loading may be easily controlled. Further more, in situ grazing incidence wide/small angle X‐ray scattering demonstrate how QD ligand surface chemistry has a pronounced effect on the self‐assembly of the nanocomposite film in terms of both small‐molecule crystallization and QD dispersion versus ordering/aggregation. The approach demonstrated here shows the important role which the degree of incorporation of an active ligand, closely related in chemical structure to the host small‐molecule organic matrix, plays in both the self‐assembly of the QD and small‐molecule components and in determining the final optoelectronic properties of the system.
Highlights
Nanocomposite films containing quantum dots (QDs) have attracted considerable attention due to their wide application in solar cells,[1] light-emitting diodes,[2] photodetectors, photon-upconversion, and recently, photon-multipliers.[8]
For the TIPS-Tc:(PbS-OA/-(0.41)tetracene-2-carboxylic acid (TET-CA)) blends, QD ordering occurs prior to TIPS-Tc crystallization and a significant proportion of the QDs exist in aggregated colloidal crystal morphologies
For the TIPS-Tc:PbS-(0.53) TET-CA blends, little QD ordering is observed, with QDs remaining largely dispersed for the entirety of the film formation process and TIPS-Tc crystallization
Summary
Nanocomposite films containing quantum dots (QDs) have attracted considerable attention due to their wide application in solar cells,[1] light-emitting diodes,[2] photodetectors, photon-upconversion, and recently, photon-multipliers.[8]. V. Gray Department of Chemistry – Ångström Laboratory Uppsala University Box 523, Uppsala 751 20, Sweden. In a small-molecule:QD nanocomposite, we have recently demonstrated significantly improved QD dispersibility (compared to native OA QD ligands) through modifying the PbS QD surface with an active, highly soluble semiconductor ligand [6,11-bis((triisopropylsilyl)ethynyl)tetracene-2-carboxylic acid (TET-CA)], which in turn allows for the QDs to be incorporated in a blend with a matched organic semiconductor 5,12-bis((triisopropylsilyl)ethynyl)tetracene.[8]. These systems are of particular interest for their potential as singlet fission photon multiplication materials (SF-PM). Our data provide real time insights into the complex self-assembly phenomena and nanoscale structure formation within organic-QD nanocomposites and pave the way for the rational design of ligand exchange protocols and solution processing conditions in order to obtain optimal nanocomposite morphologies for optoelectronic applications
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