Highly Efficient One-Dimensional Triplet Exciton Transport in a Palladium–Porphyrin-Based Surface-Anchored Metal–Organic Framework
- 2 April 2019
- journal article
- research article
- Published by American Chemical Society (ACS) in ACS Applied Materials & Interfaces
- Vol. 11 (17), 15688-15697
- https://doi.org/10.1021/acsami.9b03079
Abstract
Efficient photon harvesting materials require easy-to-deposit materials exhibiting good absorption and excited-state transport properties. We demonstrate an organic thin-film material system, a palladium-porphyrin based surface-anchored metal-organic framework (SURMOF) thin film, that meets these requirements. Systematic investigations using transient absorption spectroscopy confirm that triplets are very mobile within single crystalline domains; a detailed analysis reveals a triplet transfer rate on the order of 1010 s-1. The crystalline nature of the SURMOFs also allows a thorough theoretical analysis using density functional theory (DFT). The theoretical results reveal that the intermolecular exciton transfer can be described by a Dexter electron exchange mechanism that is considerably enhanced by virtual charge-transfer exciton intermediates. On the basis of the photophysical results, we predict exciton diffusion lengths on the order of several micrometers in perfectly ordered, single-crystalline SURMOFs. In the presently available samples, strong interactions of excitons with domain boundaries present in these metal-organic thin films limit the diffusion length to the diameter of these two-dimensional grains, which amount to about 100 nm. These results demonstrate potential of SURMOFs for energy harvesting applications.Keywords
Funding Information
- Helmholtz-Gemeinschaft
- Science Foundation Ireland (IvP 13/IA/1894)
- Deutsche Forschungsgemeinschaft (SFB 1176, SPP 1928)
- Baden-W??rttemberg Stiftung
- China Scholarship Council
- Seventh Framework Programme
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