Physics Seminars
From Exclusion to Inclusion: Controlling Quantum Dot : Organic Semiconductor Blend Morphologies for Photon Multiplication
Speaker: Daniel T. W. Toolan (University of Manchester)
Date: Wednesday 20 May 2026
Time: 15:00
Venue: N/3.28
This talk will focus on the development of nanocomposite films based on small-molecule organic semiconductors (OSCs) blended with quantum dots (QDs), with particular emphasis on how nanoscale structure, self-assembly, and morphology govern their function. Controlling the organisation of these hybrid films is central to the development of photon multipliers, a promising technology for enhancing the performance of silicon photovoltaics (Si-PV). In these materials, a high-energy photon absorbed by the organic semiconductor generates a singlet exciton, which undergoes singlet fission to form two independent triplet excitons. These triplet excitons are then transferred to the QDs and re-emitted at a lower energy, tuned to more closely match the Si-PV bandgap and thereby circumvent thermalisation losses in single-junction solar cells. I will summarise recent progress in understanding and controlling the self-assembly of these photon-multiplier materials, showing how morphology and intercomponent organisation critically determine performance, as determined via grazing-incidence X-ray scattering studies. I will discuss our work demonstrating how subtle changes to the organic semiconductor structure can strongly affect crystallisation, quantum dot dispersibility, and long-term morphological stability, and how these effects can be further tuned through ligand design and mixed-host strategies.[1,2] I will also show how in situ scattering measurements during solution coating reveal distinct assembly pathways, including cases where crystallisation proceeds directly and others where it is mediated by quantum dot aggregation, with important consequences for the final nanocomposite structure.[3] Together, these studies provide a broader framework for understanding and directing structure formation in OSC:QD, helping to define design rules for robust hybrid films across photon multiplication and related optoelectronic applications. 1. Nano Lett. 2026, 26, 4, 1274-1280. 2. J. Am. Chem. Soc. 2024, 146, 11, 7763-7770. 3. Nanoscale Horiz., 2023,8, 1090-1097.