Wednesday 1 September 2021
Time: 1pm in QLD, NSW, ACT, Vic, and Tas
11am in WA 12:30pm in NT
12:30pm in SA
3pm in New Zealand
Meeting URL: https://jcu.zoom.us/j/83033425738
Each talk is 20 minutes duration followed by approximately 5 minutes for questions and discussion.
Time (QLD time, adjust as needed)
1:00 – 1:25pm
Understanding the formation and morphology of organic semiconductor thin films at the atomic level
Audrey V. Sanzogni
The University of Queensland
Functional thin films composed of organic semiconductors are transforming opto-electronic devices ranging from light weight flexible solar cells, lighting and displays to the latest in low-cost tuneable sensor materials. The key active layers in these devices are not only amorphous but often only tens of nanometre thick meaning the morphology of the material is dominated by interfacial effects and the properties of the materials depend not only on the chemical composition, but the manner of deposition and post-manufacturing processes. Furthermore, while experimental studies on amorphous systems can provide information on bulk or averaged properties, the performance of a specific device in terms of efficiency and life-time are often dominated by variations in the local morphology. To advance the utility of organic thin film devices, we need to understand how morphology relates to performance in atomic detail.
In my talk I will show how atomistic molecular dynamics simulations in which different manufacturing processes such as vacuum deposition1 and solution processing2 are reproduced in detail are providing novel insights into how morphology affects the performance of real devices. The predictive power of these models will be demonstrated as well as how elements such as the aggregation of guest molecules in a host matrix and the potential of solvent remaining in a thin film after solution deposition (Figure 1) are providing key insights into the function and properties of organic thin films.
Figure 1: Snapshots of a solution processing simulation over time and the resulting thin film
1. Lee, T.; Sanzogni, A.; Zhangzhou, N.; Burn, P. L.; Mark, A. E., Morphology of a Bulk Heterojunction Photovoltaic Cell with Low Donor Concentration. ACS Appl. Mater. Interfaces 2018, 10 (38), 32413-32419.
2. Lee, T.; Sanzogni, A. V.; Burn, P. L.; Mark, A. E., Evolution and Morphology of Thin Films Formed by Solvent Evaporation: An Organic Semiconductor Case Study. ACS Appl. Mater. Interfaces 2020, 12 (36), 40548-40557.
1:25 – 1:50pm
Balanced Hole and Electron Transport in TCTA:Ir(ppy)3 Blends as Determined by Photo-MIS-CELIV
Mile Gao1, Paul L. Burn,1* Almantas Pivrikas2
1Centre for Organic Photonics & Electronics (COPE), School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
2Physics department, Murdoch University, Perth, Western Australia, 6150, Australia
Balanced charge injection and transport in organic light emitting diodes (OLEDs) is essential for highly efficient devices with small efficiency roll-off at high luminance. However, there are few reports on the measurement of charge mobility within the blend emissive layer of an OLED. In this presentation, we show that photoexcitation in conjunction with Metal-Insulator-Semiconductor Charge Extraction with Linearly Increasing Voltage (photo-MIS-CELIV) can be used to determine the hole and electron mobilities of the emissive blend layer in a single device architecture. We demonstrate the technique by studying the commonly used emissive blend of fac-tris[2-phenylpyridinato-C2,N]iridium(III) [Ir(ppy)3] and tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as well as neat TCTA and Ir(ppy)3 films. It was found that Ir(ppy)3 and its blend films with TCTA have measurable electron mobilities and critically they are of similar magnitude as their hole mobilities, irrespective of the Ir(ppy)3 doping ratio. Such balanced charge mobility suggests that the transport of both holes and electrons occurs mostly on the Ir(ppy)3 guest molecules in the blend. Additionally, we demonstrate that photo-MIS-CELIV can be used to measure the quantum efficiency of exciton dissociation in organic semiconductor thin films.
1:50 – 2:00pm – Questions and discussion
During the seminar:
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Please be aware that the talks will be recorded and posted on the AUCAOS website.
Previous seminars can be viewed here: https://seminars.aucaos.org.au/
Call for abstracts:
Seminars are typically held on the first Wednesday of each month.
At this time we are specifically encouraging HDR students to present their work to broad audience. If you are interested in speaking then please submit an abstract to firstname.lastname@example.org.