Ultra-Thin Transition Metal Dichalcogenides for Solar Energy Conversion: Towards Efficient, Low Cost Devices
Literature seminar abstract
Transition metal dichalcogenides (TMDs) have been shown to be highly efficient materials for photoelectrochemical solar energy to electricity and chemical fuel conversion.1 Due to their unique layered structure, bulk TMD crystals can be easily exfoliated into single and multilayer thick flakes and deposited on to conducting substrates. However, electrodes made from exfoliated TMD thin films are far less efficient than devices made from bulk crystals.2 It is critical to understand the underlying material properties that cause this performance gap to develop high efficiency exfoliated TMD electrodes. Towards this goal, two groups have recently used distinctly different approaches to study the effects of the dimensions of exfoliated TMD nanoflakes on photocurrent generation efficiency. Kevin Sivula and co-workers used a combined size-selective synthesis and ensemble average photoelectrochemical approach to investigate the role of nanoflake thickness and lateral dimensions of exfoliated WSe2 on photocurrent generation efficiency. The authors used a combination of size dependent photocurrent measurements and charge carrier transport simulations to conclude that a balance between nanoflake thickness and width will lead to optimal performance. In summary, the authors propose optimum nanoflake thickness and width of 15-20 nm and 700 nm, respectively.3 In contrast, Robert Dryfe and co-workers employed a single nanoflake approach to correlate MoS2 nanoflake thickness with photocurrent generation efficiency, claiming that external quantum efficiency increases with increasing nanoflake thickness.4 Here, I will present unpublished single nanoflake photocurrent microscopy results and discuss why the major conclusions of these papers contradict each other.
(1) Tenne, R.; Wold, A. Appl. Phys. Lett. 1985, 47, 707-709.
(2) Yu, X.; Prévot, M. S.; Guijarro, N.; Sivula, L. Nat. Commun.. 2015, 6, 1-8.
(3) Yu, X.; Sivula, K. Chem. Mater. 2017, 29, 6863-6875.
(4) Velický, M.; Bissett, M. A.; Woods, C. R.; Toth, P. S.; Georgiou, T.; Kinloch, I. A.; Novoselov, K. S.; Dryfe, R. A. W. Nano. Lett. 2016, 16, 2023-2032.
Speaker: Allan Isenberg
Speaker Institution: Colorado State University
Event Date: 09-22-2017
Event Time: 4:00 PM
Event Location: Chemistry A101
Mixer Time: 3:45 PM
Mixer Location: Chemistry B101E
Host: J. Sambur