Online Seminar Announcement: Wednesday 7 July 2021

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

Time:
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

Seminar schedule
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
Victoria University of Wellington

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.
2. S. Chandrabose, K. Chen, A. J. Barker, J. J. Sutton, S. K. K. Prasad, J. Zhu, J. Zhou, K. C. Gordon, Z. Xie, X. Zhan and J. M. Hodgkiss, J. Am. Chem. Soc., 2019, 141, 6922.
3. P. A. Hume and J. M. Hodgkiss, J. Phys. Chem. A, 2020, 124, 591

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
2Energy and Resources Institute, Charles Darwin University, 0909 Darwin, NT, 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 [1]. 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. [2]
The characterisation of exciton generation is carried out in three BHJ OSCs, OSC1: an inverted NF BHJ OSC, OSC2: a conventional NF BHJ OSC and OSC3: a conventional fullerene BHJ-OSC. It is found that the overlap of the regions of strong constructive interference of incident and reflected electric fields of electromagnetic waves and those of high photon absorption within the active layer depends on the active layer thickness. An optimal thickness of the active layer can thus be obtained at which this overlap is maximum. We have simulated the rates of total exciton generation and position dependent exciton generation within the active layer as a function of the thicknesses of all the layers in all three OSCs and optimised their structures. Based on our simulated results, the inverted NF BHJ OSC1 is found to have better short circuit current density which may lead to better photovoltaic performance than the other two. [2]

[1] 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.
[2] Sreedhar Ram K, Mehdizadeh-Rad H, Ompong D, Setsoafia DDY, Singh J. Characterising Exciton Generation in Bulk-Heterojunction

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

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.


AUCAOS 2021

AUCAOS 2021 is planned to take place in Tweed Heads, New South Wales, Australia from Sunday 28th November to Wednesday 1st December 2021.

In the event that a traditional single-venue meeting is not possible due to travel restrictions, the symposium will instead take place at local nodes across Australia, with presentations streamed live.

For more details please click here.


Online Seminar Announcement: Wednesday 5 May 2021

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 5 May 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

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/84611488938

Seminar schedule
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 The Effects of Deposition Technique on Charge and Exciton Dynamics in OLEDs – A Computational Study

Stephen Sanderson
James Cook University & The University of Queensland

Solution-processed OLED films present a number of advantages in cost and scalability over their vacuum-deposited counterparts. However, they currently do not meet the same performance standards, tending to degrade at a faster rate. Towards understanding this, kinetic Monte-Carlo transport modelling combined with molecular dynamics deposition modelling offers a detailed picture of device operation, and allows for the establishment of structure-property relationships that can be difficult to observe through other means. This presentation gives an overview of KMC modelling techniques in the context of phosphorescent OLEDs, along with an outline of techniques developed for building thicker solution-deposited films without the need for prohibitively large initial systems. Using these techniques, a comparison is made between charge and exciton dynamics in solution- and vacuum-deposited OLED films with the goal of gaining insight into the cause of experimentally observed differences in degradation rate.

1:25 – 1:50pm Ternary Strategy and Burn-in Degradation Investigation of Organic Solar Cells

Leiping Duan
The University of New South Wales

Organic solar cells (OSCs) as a low-cost new generation of renewable energy technology have become a promising contender that could serve as an alternative to silicon to established photovoltaic (PV) technologies in the future. Meticulous active layer engineering is a crucial element for OSCs to improve the device performance, where the application of the ternary strategy is an effective pathway. The ternary strategy retains the simplicity of the fabrication for organic solar cells and exhibits a higher potential towards large-scale fabrication. Investigating the novel application of ternary strategy in OSCs is a promising method towards higher device performance. Apart from the pursuit of the device performance, research for the long-term OSCs device stability is also critical for its practical applications and future commercialization. Burn-in degradation has become an ineluctable barrier for OSCs to achieve long-time stability, where an in-depth understanding of the mechanism behind burn-in degradation has become the precondition to conquer this barrier.
The aim of research works in my PhD thesis is to improve the performance of OSCs and provide understandings of its degradation mechanism behind. The ternary strategy, especially incorporated with novel non-fullerene acceptor materials, as a performance improving method, is the primary focal point in this thesis. In this thesis, we derived three novel ternary OSCs and provided a comprehensive investigation of the mechanism behind its performance enhancement. On the other hand, this thesis also systematically investigated the burn-in degradation mechanism in OSCs. We analysed the degradation mechanism based on each instability factor including light, heat, and air, to gain in-depth understating. Moreover, combined with the application of ternary strategy and the burn-in degradation study, we did a case study of the burn-in degradation in the high-efficiency PTB7-Th: COi8DFIC: PC71BM ternary OSCs. We found that the ternary strategy could increase the stability of the device, and the burn-in degradation mechanism in ternary OSCs is more dependent on its dominant binary counterpart. Overall, insights gained in this work into the nature of ternary strategy and burn-in degradation provide a step for OSCs towards large scale application and future commercialization.

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

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.


Online Seminar Announcement: Wednesday 7 April 2021

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 April 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

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/86449047647

Seminar schedule
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 Organic Polariton Lasing with Molecularly Isolated Perylene Diimides

Dr. Girish Lakhwani
Sydney University

In the last decade, strong light matter coupling has become an alternative path to achieve lasing in organic materials via use of polaritons. Polariton lasers do not require population inversion and thus hold the promise of lower laser thresholds. Organic materials are particularly suited for polariton lasing as their large absorption coefficients result in impressive exciton-photon couplings strengths at room temperature. Here I will demonstrate polariton lasing in a molecularly isolated perylene diimide. [1,2] The emission exhibits threshold behaviour, spatial coherence, and the characteristic blue-shifting of polariton systems. We expect perylene dyes will become a useful polariton laser class.

1. Sabatini et al. J Mater Chem C, 7, 2954 (2019)
2. Sabatini et al. Appl. Phys. Lett, 117, 041103 (2020)

1:25 – 1:50pm Optimal quantum dot size for photovoltaics with fusion

Dr. Laszlo Frazer
Monash University

Light fusion increases the efficiency of solar cells by converting photons with lower energy than the bandgap into higher energy photons. The solar cell converts the produced photons to current. We use Monte Carlo simulation to predict that lead sulfide quantum dot sensitizers will enable fusion with a figure of merit on the mA/cm^2 scale, exceeding current records, while enabling silicon cell compatibility. Performance is highly sensitive to quantum dot size, on the order of mA/cm^2/nm.

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

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.


Online Seminar Announcement: Wednesday 10 March 2021

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 10 March 2021

Time:
1pm in QLD
2pm in NSW, ACT, Vic and Tas
11am in WA
12:30pm in NT
1:30pm in SA
4pm in New Zealand

Click this link to join the meeting: https://jcu.zoom.us/j/81590417076

Seminar schedule
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 N-Heterocyclic Carbene Platinum(II) Dialkynyl Complexes – A New Class of Highly Tunable and Efficient Emitter Systems

Assoc. Prof. Koushik Venkatesan
Macquarie University

New and efficient light-emitting materials are required for a broad range of potential applications in the fields of sensors, storage, photoelectronic devices, and optical devices. Extensive investigations on transition metal complexes as triplet emitters for application in phosphorescent organic light emitting devices (PhOLEDs) have been carried out. Metal complexes with specific ligand environment allow to tailor the luminescent properties in a precise fashion for a specific application. Achieving high stability, high quantum efficiency and specific chromaticity remains a major challenge in this field. Recently, our group has demonstrated a series of highly emissive platinum(II) complexes bearing N-heterocyclic carbene ligands with promising photophysical properties. Further building on this work, we have developed new series of small molecules and investigated their detailed luminescent properties. Selected molecules that have been fabricated into devices show high potential for applications in light emitting devices.

1:25 – 1:50pm Classification of Coherent Enhancements of Light-Harvesting Processes

Assoc. Prof. Ivan Kassal
The University of Sydney

Several kinds of coherence have recently been shown to affect the performance of light-harvesting systems, in some cases significantly improving their efficiency. Recently, we classified the possible mechanisms of coherent efficiency enhancements [1], based on the types of coherence that can characterize a light-harvesting system and the types of processes these coherences can affect. We show that enhancements are possible only when coherences and dissipative effects are best described in different bases of states. In addition, our classification allows us to predict a previously unreported coherent enhancement mechanism.

I will discuss the implications of this classification for the field of organic photovoltaics. Several coherent mechanisms have been proposed for boosting OPV efficiency, but most of them are impossible. A few manifestations of coherence may matter, including one that we are confident plays a big role in OPV performance [2].

[1] Stefano Tomasi and Ivan Kassal, J. Phys. Chem. Lett. 2020, 11, 2348–2355.

[2] Daniel Balzer, Thijs J.A.M. Smolders, David Blyth, Samantha N. Hood, and Ivan Kassal, Chem. Sci. doi:10.1039/D0SC04116E (2021).

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

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.


Online Seminar Announcement: Wednesday 3 February 2021

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 3 February 2021

Time:
1pm in QLD
2pm in NSW, ACT, Vic and Tas
11am in WA
12:30pm in NT
1:30pm in SA
4pm in New Zealand

Click this link to join the meeting: https://jcu.zoom.us/j/89897826579

Seminar schedule
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 A flexible organic solar cell based on doped graphene/PET substrate

Dr. Hellen Jin
The University of Queensland

Graphene has shown tremendous potential as a transparent conductive electrode (TCE) for flexible organic solar cells (OSCs). However, the trade-off between electrical conductance and transparency as well as surface roughness of the graphene TCE with increasing layer number limits power conversion efficiency (PCE) enhancement and its use for large-area OSCs. Here, we use a 300 nm-thick poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c]-[1,2,5]thiadiazole)]:[6,6]-phenyl-C71-butyric acid methyl ester as the photoactive layer and a benzimidazole (BI)-doped graphene as the transparent anode to demonstrate efficient OSCs with good flexibility. It is found that 3 layer (L) graphene had the best balance between sheet resistance, optical transmittance and surface roughness for optimized cell design. A 0.2 cm2 cell with a 3L BI-doped graphene anode achieves a PCE of 6.85%, which is one of the highest PCE values reported so far for flexible graphene anode-based OSCs. The flexible cells are robust, showing only a small performance degradation during up to 250 flexing cycles. Moreover, the combination of the thick photoactive layer with the optimized 3L BI-doped graphene TCE enabled production of 1.6 cm2 flexible OSCs with a PCE of 1.8%. Our work illustrates the importance of graphene TCE development for flexible OSCs as well as other wearable optoelectronic devices.

1:25 – 1:50pm Carbene-metal-amides as emitting materials in high-efficiency organic light-emitting diodes

Dr. Patrick Conaghan
University of Sydney / University of Cambridge

Emitting materials in organic light-emitting diodes are predominantly phosphorescent iridium complexes or all-organic thermally activated delayed fluorescence materials. We have demonstrated that the carbene-metal-amide molecular structure of coinage-metal complexes can also be used to produce organic light-emitting diodes with efficient electroluminescence from both singlet and triplet excited states.
We have shown that the emission colour can be changed through variation of the electron-donating strength of the donor moiety and the polarity of the host environment and have used both of these effects to produce devices with emission across the visible range. By engineering excited state energies we have fabricated green-emitting devices with a maximum electroluminescence quantum efficiency of 26.9 % and blue-emitting devices (Commission Internationale de l’Éclairage co‐ordinates [0.17, 0.17]) with external quantum efficiency of 20.9 %.
Transient photoluminescence measurements at varying temperatures show that the emission process is thermally activated with short excited-state lifetimes (<1 μs) and along with device data show that the energy of local triplet excited states imposes an energy limit on efficient emission. Carbene-metal-amides do not show a strong concentration-dependent luminescence quenching in the solid state, which has allowed us to fabricate host-free devices with external quantum efficiency of up to 23 % which, to our knowledge, is the highest reported for host-free organic light-emitting diodes.

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

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.


Online Seminar Announcement: Wednesday 2 December 2020

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 2 December 2020

Time:
1pm in QLD
2pm in NSW, ACT, Vic and Tas
11am in WA
12:30pm in NT
1:30pm in SA
4pm in New Zealand

Click this link to join the meeting: https://jcu.zoom.us/j/84452910435

Seminar schedule
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 Non-Toxic Hybrid Inorganic-Organic Chromophores for the Advancement of Luminescent Solar Concentrators

Calum Gordon
Victoria University of Wellington

Luminescent solar concentrators (LSCs) consist of a waveguide medium containing light harvesting chromophores of an inorganic or organic nature. These chromophores absorb incoming light, and radiatively re-emit light, which is propagated to the edges of the LSC by the waveguide. The concentrated light at the edges is then collected by coupled solar cells.
The advantages of LSCs coupled to solar cells relative to stand alone solar cells are that LSCs are cheaper, and can capture indirect sunlight.
A pressing issue with modern LSCs are re-absorption events by the chromophore, which dampens their efficiency. This is due to overlap between the absorbance and emission spectra of the chromophore.
By coupling inorganic and organic components together, Förster resonance energy transfer (FRET) may be achieved between the two components, creating a donor-acceptor system. The donors absorbance spectrum is sufficiently separated from the acceptors emission spectrum, mitigating re-absorption events.

1:25 – 1:50pm Magnetic field effect on UC-TTA

Elham Gholizadeh
The University of New South Wales

Solar light contains many wavelengths, but solar cells cannot absorb all those wavelengths. In fact, those photons which do not have enough energy to be absorb by the band gap will be wasted. One of the strategies that have been used until now in terms of using low energy photons is Triplet-Triplet Annhilation upconversion (UC-TTA). In this process two low energy photons will convert to a higher energy photon.
In terms of improving solar cells efficiency, it is important to make an upconversion system which convert photons below the bandgap to the photons that absorb by the solar cell. Also, since most of the upconversion system does not work in oxygen environment, finding a solution for this problem looks essential.
In my PhD, I could do UC-TTA from below the silicon bandgap in oxygen mediated environment. In this system, opposite other UC-TTA systems, oxygen improves the upconversion efficiency. So, in terms of understanding the mechanism of UC-TTA in our system in the presence of oxygen, magnetic field effect on TTA process was used. We also considered magnetic field effect on two well known UC-TTA system to be able to modify Merrifield equation and the data was fitted by this equation.

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

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.


Online Seminar Announcement: Wednesday 4 November 2020

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 4 November

Time:
1pm in QLD
2pm in NSW, ACT, Vic and Tas
11am in WA
12:30pm in NT
1:30pm in SA
4pm in New Zealand

Click this link to join the meeting: https://jcu.zoom.us/j/86786170885

Seminar schedule
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 Partial Delocalisation Enhances the Efficiency of Charge Separation in Organic Photovoltaics

Daniel Balzer
The University of Sydney

In organic photovoltaics, the question of how charges are able to overcome their significant coulombic attraction and separate has attracted heated debate. In particular, the low dielectric constants in organic semiconductors produce coulombic barriers that are an order of magnitude greater than the available thermal energy. One of the proposed answers is delocalisation, including arguments that the increased separation of charges in the CT state reduces the coulombic barrier. However, it turns out that delocalisation stabilises the CT state and increases the coulombic barrier, and therefore any benefit provided by delocalisation must come from non-equilibrium kinetic effects. However, charge separation is a two-body problem involving the correlated motion of an electron and a hole, meaning that the computational difficulty is roughly the square of the single-body mobility calculation, meaning that a fully quantum-mechanical treatment has so far proved intractable in three dimensions. A complete kinetic model would help settle the debate about the main drivers of charge separation, and unite the proposed mechanisms including delocalisation, entropy and energy gradients. Last year, we presented delocalised kinetic Monte Carlo (dKMC), the first three-dimensional model of partially delocalised charge and exciton transport in materials in the intermediate disorder regime. Here, we use dKMC to make the charge separation problem computationally accessible, allowing the first simulation of the full dynamics (and, therefore, efficiency) of charge separation in the presence of disorder, delocalisation, polaron formation and noise. We find that small amounts of delocalisation can produce large enhancements in the efficiency at which charges separate.

1:25 – 1:50pm Spatially Correlated Quantum Properties in Organic Light Emitting Diodes

William Pappas
The University of New South Wales

Electronic spin is a quantum mechanical property that is fundamental to the charge-light conversion processes in optoelectronic devices. The suppression of interactions between spins in organic semiconductors leads to relatively long relaxation times (μs) and results in the formation of weakly coulombically bound electron-hole pairs. The ability to access and modulate the spin polarisation of these pairs enhances the quantum efficiencies of device DC observables (current, luminosity), while also enabling unique functionality in spin-logic devices.
In organic light-emitting diodes, the study of spin-dependent processes giving rise to magnetic field effects have been treated monolithically. We have incorporated optical imaging microscopy into a traditional magneto-electroluminescence (MEL) setup that has allowed us to discern the intra-device variation of the quantum property (hyperfine interaction) which is responsible for these effects. We investigated the correlations between these local hyperfine field strengths in both the spatial and temporal domains. Magnetic resonance measurements are then used explain the origin of variations in the MEL lineshapes.
This work is an important step in characterising the homogeneity of spin-dependent properties in organic materials which critically control the ability to manipulate spins in organic spintronic devices.

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

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.