Proceedings of nanoGe September Meeting 2017 (NFM17)
Publication date: 20th June 2016
Excitons are ubiquitous in optoelectronic applications of inorganic quantum dots (QD) and organic semiconductor molecules (OSC) alike, but their nature is significantly distinct in these two classes of materials. Efficient dielectric screening in QDs leads to the formation of Wannier-Mott excitons with large radii and small dissociation energies. In contrast, small Frenkel excitons with large binding energies are formed in OSCs upon optical excitation. The distinct character of these two types of excitons invokes fundamental dissimilarities in the mechanism and probability of formation of excitons with different spin states. While the occurrence of singlets, triplets, charge-transfer states and excited state dimers (“excimers”) is well understood individually for each material class, an entirely new question is how readily these excitons are formed at the QD/OSC interface.
In this presentation, I will show that the concept of coupled organic-inorganic nanostructures (COIN) provides an ideal tool to study and exploit such interfacial excitons. [1] A typical material consists of periodically alternating QDs and monolayers of coordinating OSCs at the QD surface, which act as electronic coupling agents to promote charge carrier transport across the lattice of QDs. [2-4] I will demonstrate how PbS QDs are utilized as sensitizers to convert near infrared photons into singlets, triplets or excimers in the OSC monolayers as well as how their probability of formation and lifetime depends on the type of OSC.
The application potential for photon upconversion and spin-selective transport in thin films will be discussed.
References
[1] Scheele, M., Bruetting, W. & Schreiber, F. Phys. Chem. Chem. Phys. 17 (2015), 97–111.
[2] André, A., Scheele, M. et al. Chem. Mater. 27 (2015), 8105–8115.
[3] Scheele, M. Alivisatos, A.P. et al. ACS Nano 8 (2014), 2532–2540.
[4] André, A., Scheele, M. et al. Chem. Comm. 53 (2017), 1700-1703.
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