Due to the cancellation of many scientific conferences, the AUCAOS committee is pleased to announce an online seminar series. We intend to run seminars on the first Wednesday of every month until normal conferences can resume.
Date: Wednesday 7 July 2021
1pm in QLD, NSW, ACT, Vic, and Tas
11am in WA
12:30pm in NT
12:30pm in SA
3pm in New Zealand
Please note different times in some states due to the end of daylight savings time.
Click this link to join the meeting: https://jcu.zoom.us/j/84054173062
Each talk is 20 minutes duration followed by approximately 5 minutes for questions and discussion.
|Time (QLD time, adjust as needed):||Presentation:|
|1:00 – 1:25pm|| Structural origins of long-range exciton diffusion in a non-fullerene acceptor
Dr Paul Hume
In organic photovoltaic cells, absorption of light leads to the formation of excitons, which then diffuse to the donor/acceptor interface to generate photocurrent. The distance from which excitons can reach the interface is constrained by the exciton diffusion length, which has been difficult to quantitatively model or predict due to structural and energetic disorder. Modern non-fullerene acceptors have been shown to possess exceptionally large diffusion lengths, along with well-defined molecular and packing structures, suggesting that a predictive framework for materials design and computational screening may be possible.
We recently demonstrated1 that the large diffusion coefficient observed experimentally2 in an archetypical non-fullerene acceptor, IDIC, can be accurately quantified using density functional theory, and that the low energetic disorder means that the crystal structure provides a meaningful starting point to understand exciton motion in thin films. By accounting for short- and long-range excitonic interactions3, as well as spatiotemporal disorder, we can accurately predict experimental values for exciton diffusivity and diffusion length. The simplicity and accuracy of this approach are directly linked to the structural order of these materials, and an electronic coupling profile that is unusually resilient to thermal distortions – highlighting the potential for computational materials screening. Moreover, we show that these factors, combined with the low reorganisation energy and significant long-range electronic coupling, lead to diffusion rates that approach the upper limit of incoherent energy transfer, and long diffusion lengths that relieve constraints on organic solar cell device architectures.
1. P. A. Hume, W. Jiao, and J. M. Hodgkiss, J. Mater. Chem. C 2021, 9, 1419.
|1:25 – 1:50pm||Characterising Exciton Generation in Bulk-heterojunction Organic Solar Cells
Kiran Sreedhar Ram1
1College of Engineering, IT and Environment, Purple 12, Charles Darwin University, Darwin, NT 0909, Australia
The research and development in the field of organic solar cells (OSCs) have been thriving over the last few decades due to being of low cost, light weight and flexibility compared to the inorganic solar cells (ISCs). However, there are two major challenges in bringing OSCs to the commercial stage: i) low power conversion efficiency (PCE) and ii) low stability or degradation . Bulk-heterojunction (BHJ) OSCs with an active layer based on fullerene acceptor have currently dominated the research activities in organic photovoltaic because of their excellent charge transport properties. However, fullerene acceptor materials have some disadvantages which include limited chemical and energetic tunability, narrow range of absorption spectra and unstable morphology thereby limiting the overall PCE and stability of the devices thus fabricated. Therefore, the research focus has moved to the use of non-fullerene (NF) acceptors in BHJ OSCs. In this research, work has been done in understanding the characteristics of exciton generation in conventional and inverted NF acceptor based BHJ OSCs and the results are also compared to fullerene acceptor based BHJ OSCs. 
 K. S. Ram and J. Singh, “Highly Efficient and Stable Solar Cells with Hybrid of Nanostructures and Bulk Heterojunction Organic Semiconductors,” Advanced Theory and Simulations, vol. 2, no. 6, p. 1900030, 2019/06/01 2019, doi: 10.1002/adts.201900030.
|1:50 – 2:00pm||Open discussion|
During the seminar:
- Please keep your microphone muted unless you are speaking. This is to reduce the background noise and avoid disrupting the presenter.
- You will be automatically muted when you join the virtual meeting room. To speak, you will need to unmute yourself by using the audio controls in the lower left of the Zoom window.
- If you have not used Zoom before, then it is recommended that you join 5 minutes before the starting time to ensure that you have your software set up correctly.
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 held on the first Wednesday of each month.
In the spirit of building a community in these challenging times, you are encouraged to give a talk. Do you have a talk that you would have given at a conference that was cancelled? Please consider adapting that talk for this format.
Submit abstract by email to bronson[dot]philippa[at]jcu[dot]edu[dot]au.