Ligand Directed Self-Assembly of Bulk Organic-Semiconductor/Quantum-Dot Blend Films: Towards Efficient Triplet Exciton-Photon Interconversion in the Solid State

Victor Gray^a^,^b, Daniel Toolan^c^,^d, Simon Dowland^e, Jesse Allardice^b, Michael Weir^f, Zhilong Zhang^b, James Xiao^b, Anastasiia Klimash^h, Jurjen Winkel^e, Emma Holland^g, Garrett Fregoso^g, John Anthony^g, Hugo Bronstein^h, Richard Friend^b, Anthony Ryan^d, Richard Jonesⁱ, Neil Greenham^b, Akshay Rao^b

^aDepartment of Chemistry—Ångström Laboratory, Uppsala University, SE 751 21 Uppsala, Sweden

^bCavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom

^cDepartment of Materials, The University of Manchester, Oxford Road, United Kingdom

^dDepartment of Chemistry, The university of Sheffield

^eCambridge Photon Technology, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK

^fSchool of Physics and Astronomy, University of Nottingham, NG7 2RD, U.K.

^gCenter of applied research, University of Kentucky

^hYusuf Hamied Department of Chemistry, University of Cambridge; Lensfield Road, Cambridge, UK

ⁱJohn Owens Building, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2024 Conference (MATSUS24)

#SF-TF - Singlet Fission and Triplet Fusion

Barcelona, Spain, 2024 March 4th - 8th

Organizer: Jonas Sandby Lissau

Invited Speaker, Victor Gray, presentation 044
DOI: https://doi.org/10.29363/nanoge.matsus.2024.044
Publication date: 18th December 2023

Quantum dot-organic hybrids have become popular as triplet-photon converting systems, for example as triplet sensitizers for triplet-triplet annihilation photon upconversion and photon multiplication based on singlet fission.[1] The organic ligand in such hybrid structures plays a crucial role in mediating triplet exciton transfer between the organic molecules and inorganic quantum dots in solution, and many studies have studied the intricate details of triplet mediation via the ligand.[2] Here I will higlight another aspect of the ligand, namely as a directing agent in bulk organic-semiconductor/quantum-dot blend films. These blends, comprising organic semiconductors and inorganic quantum dots are relevant for many optoelectronic applications and devices. However, the individual components in organic-QD blends have a strong tendency to aggregate and phase separate during processing to form films, compromising both their structural and electronic properties. Here, I will explain how a suitable organic ligand can achieve well-dispersed inorganic-organic blend films, as characterised by X-ray and neutron scattering and electron microscopy. As proof-of-concept I will show two examples of these films applied to singlet fission based photon multiplication[3] and triplet-triplet annihilation based photon upconversion. Due to the optimal blend morphology triplet excitons can be transferred with near unity efficiently across the organic-inorganic interface, while the TIPS-tetracene films maintain efficient SF (190% yield) in the organic phase, resulting in 95% of the triplet excitons generated via SF in the organic phase being harvested by the QDs. By changing the relative energy between organic and inorganic components yellow upconverted emission is observed upon 790 nm NIR excitation. Overall, this talk will exemplify a highly versatile approach to overcome long-standing challenges in the blending of organic semiconductors with QDs with relevance for many optical and optoelectronic applications.

References:

[1] Gray, V., Allardice, J., Zhang, Z., Rao, A., Organic-quantum dot hybrid interfaces and their role in photon fission/fusion applications, Chem. Phys. Rev., 2021, 2, 031305.

[2] Zihao, X., Huang, Z., Tao, J., Lian, T., Tang, M.L., Mechanistic Understanding and Rational Design of Quantum Dot/ Mediator Interfaces for Efficient Photon Upconversion, Acc. Chem. Res., 2020, 54, 70-80.

[3] Allardice, J., et al., Ligand Directed Self-Assembly of Bulk Organic-Semiconductor/Quantum-Dot Blend Films Enables Near Quantitative Harvesting of Triplet Exciton, 2020, arXiv:2009.05764

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