The Role of the Supramolecular and Electronic Structure in the Performance of Molecular Diodes
Prof. Christian A. Nijhuis
Chemistry Department, National University of Singapore
http://staff.science.nus.edu.sg/~christiannijhuis/index.html
17:00 - 18:00 Tuesday 27 October 2015 KFU HS 5.01 Understanding the mechanisms of charge transport across molecules, or self-assembled monolayers, is important in organic based photovoltaics, OLEDs, energy storage, bio-electronic devices, etc. Physical-organic studies that connect the supramolecular structure of the device to device performance are challenging.[1,2]
During the talk I will discuss our recent progress in the development of molecular tunnel junctions based on self-assembled monolayers (SAMs). We form SAM-based molecular junctions using top-electrodes of a non-invasive liquid-metal that forms stable features in microchannels.[3] This liquid-metal alloy (a mixture of Ga and In stabilized by a conductive 0.7 nm thick layer of GaOx) forms good electrical contacts with SAMs. This platform makes it possible to perform detailed physical-organic studies of charge transport across SAMs and to address some long standing controversies in the field. For instance, our studies made it possible to connect the large spread in the tunneling decay coefficient β and injection currents to the presence of defects.[4,5] We found several ways to minimize defects and we developed new characterization tools to study defects directly. I will also describe how the self-repair mechanisms of SAMs help to improve the quality of the junctions. These lessons we apply to construct molecular diodes that perform well by fine-tuning the molecule—electrode coupling and the supramolecular structure of SAMs with ferrocene units.[6-9]
References
1) F. C. Simeone, H. J. Yoon, M. M. Thuo, J. R. Barber, B. Smith, G. M. Whitesides, J. Am. Chem. Soc. 2013, 135, 18131
2) Tan, S. F.; Wu, L.; Yang, J. K. W.; Bai, P.; Bosman, M.; Nijhuis, C. A. Science, 2014, 343, 1496-1499
3) Wan, A.; Jiang, L.; Suchand Sangeeth, C. S.; Nijhuis, C. A. Adv. Funct. Mater. 2014, 24, 4442.
4) Yuan, L.; Jiang, L.; Zhang, B.; Nijhuis, C. A. Angew. Chem. Int. Ed. 2014, 53, 3377.
5) Jiang, L.; Suchand Sangeeth, C. S.; Wan, A.; Vilan, A.; Nijhuis, C. A. J. Phys. Chem. C 2015, 119, 960
6) Nerngchanmnong, N.; Yuan, L.; Qi, D. C.; Jiang, L.; Thompson, D.; Nijhuis, C. A. Nat. Nanotechnol. 2013, 8, 113
7) Jiang, L.; Yuan, L.; Cao, L.; Nijhuis, C. A. J. Am. Chem. Soc. 2014, 136, 1982
8) Yuan, L.; Breuer, R.; Jiang, L.; Schmittel, M.; Nijhuis, C. A. Nano Lett. 2015, 15, 5506.
9) Yuan, L.; Nerngchamnong, N.; Cao, L.; Hamoudi, H.; Del Barco, E.; Roemer, M.; Sriramula, R.; Thompson, D.; Nijhuis, C. A. Nat. Commun. 2015, 6, 6324.
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