Online Seminar Announcement: Wednesday 2 March 2022

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

Meeting URL: https://jcu.zoom.us/j/81155055049

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

Materials Intermixing and the Dipole Formation at the active Layer/Conjugated Polymer P(NDI3N-T-Br) Interface

Amira R Alghamdi

Flinders University

Interfacial engineering using interface layers has been identified as an essential approach for maximizing power conversion efficiency (PCE) of polymer solar cells (PSCs) by optimizing the charge transport between the active layer and the charge extracting electrodes through aligning the energy levels between the layers in a device. The properties of an interface layer have to allow for the transport of one of the charge carriers and at the same time block the other. As an example, the interface layer helping to extract the electrons from the active layer should block the transport of the holes to the same interface layer. P(NDI3N-T-Br) polymer was used as a cathode interface layer in inverted organic solar cells (OSCs) fabricated using poly[2,3-bis(3- octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) and poly[[N,N’-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] (N2200) as the donor and acceptor materials, respectively. The aim of the work is to determine the position of the energy levels of P(NDI3N-T-Br) to those of the materials forming the active layer, resulting in a physical and electronic model of the interface region. We show that these quantities can be derived from the electron spectroscopy data when a full component analysis of the valence electron spectra is conducted. The valence electron spectroscopy technique shows that a dipole formed at the interface between TQ1, and P(NDI3N-T-Br) blocks the transfer of holes from the active layer to the P(NDI3N-T-Br). However, the transfer of electrons from N2200 is facilitated.


Presentation
1:25 – 1:50pm

Investigating the long-term stability of organic light emitting diodes by Rutherford backscattering technique

Tengfei Qiu

The University of Queensland

Phosphorescent organic light emitting diodes (P-OLEDs) are a promising display technology due to the high colour purity and quantum efficiency. The long-term stability is one of the major issues for these devices. In a typical P-OLED structure, the emissive layer containing phosphorescent molecules is sandwiched by several electron transport layers and hole transport layers. Physical changes in the film structure caused by interlayer material diffusions dramatically changed the photoelectric properties. Obvious changes in material density and thickness under rapid annealing conditions to temperatures higher than the glass transition temperatures of the materials can be detected by neutron reflectometry (NR). Corresponding changes in emitting properties can be reflected in the photoluminescent (PL) spectra. However, performance degradations happen in the course of normal operational conditions for display applications, where temperatures higher than room temperature and lower than 60 ° C are more likely to be encountered. Under such mild conditions, the minor changes in material density and thickness are difficult to detect. There is a lack of methods to detect such diffusion and further to clarify the causes of the changes in the PL spectra. Here, we use the Rutherford backscattering technique, which is able to detect the distribution of heavy metal element of phosphorescent molecules in the organic matrix to study the role of the diffusion of the phosphorescent molecules on the long-term stability of OLED devices. The work provides a new approach for investigating the performance degradation mechanism of OLEDs


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 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 bronson.philippa@jcu.edu.au.


AUCAOS members awarded research funding by Australian Research Council (Discovery Projects 2022 round 1)

Congratulations to the following AUCAOS members who have recently been awarded Discovery Project funding by the Australian Research Council:

Professor Mats Andersson, Professor Paul Burn, Associate Professor Ivan Kassal, Professor David Lewis, Professor Paul Low, Emeritus Professor Alan Mark, Professor Dane McCamey, Dr Paul Shaw, Professor Ronald White.

Please see below for further details (AUCAOS members in bold):

Investigator(s) Summary
Professor Mats Andersson; Professor David Lewis Develop materials for stable and efficient printed polymer solar cells. The project aims to develop strategies to overcome current limitations of polymer solar cells by enhancing the thermal stability of these devices. This project expects to generate new knowledge in the area of stable and high-performance polymer solar cells, that can be manufactured by the printing industry in Australia. The expected outcome of this project includes new high performing materials, processing and additive strategies to overcome the key challenge to commercialising polymer solar cells. A significant benefit is their printability, providing the opportunity to establish a sovereign capability to manufacture low cost energy production systems in Australia.
Professor Paul Burn; Emeritus Professor Alan Mark; Dr Paul Shaw Validation of predicted solution processed organic semiconductor properties. Controlling organic semiconductor film morphology at a molecular level is key to advancing the performance of optoelectronic devices such as large area organic light-emitting diode lighting, solar cells and sensors. The project aims to move from an empirical design cycle of material synthesis, device fabrication and testing to a more predictive approach where morphologies from molecular simulations are used to rationalise differences in experimentally measured optoelectronic properties. Outcomes will include unique insight into atomic-level structural details that determine device efficiency and an understanding of whether atomic simulations can be applied to accelerate improvements in device performance and translation to industry.
Associate Professor Ivan Kassal PCharge and energy transport in disordered functional materials. This project aims to understand how energy and electric charge move through disordered materials. Many next-generation materials—including organic semiconductors, hybrid perovskites, and conductive metal-organic frameworks—promise better solar cells, sensors, and electrocatalysts; however, they remain incompletely understood because they are disordered and noisy systems that are difficult to describe mathematically. This project expects to develop the first theoretical techniques that capture all essential features of transport in disordered materials. The resulting understanding of structure-function relationships should accelerate the rational design of cutting-edge devices for energy conversion and storage.
Professor Paul Low; Professor Colin Lambert; Professor Richard Nichols Molecular Thermoelectric Materials: A New Hot Topic. This project aims to use the principles of chemistry and molecular electronics to synthesize and study molecules able to directly convert waste heat into electricity through the Seebeck effect. This project expects to generate new knowledge concerning the wire-like properties of molecules and conditions that lead to a high Seebeck coefficient, together with interference effects to suppress thermal conductance. Expected outcomes of this project include a deeper understanding of chemical structure – molecular electronic property relationships, and enhanced international collaboration with the UK. This should provide benefits in terms of low-cost conversion of waste heat to electrical energy.
Emeritus Professor Alan Mark; Dr Martin Stroet; Professor Chris Oostenbrink; Professor Gunnar Klau Enhanced force fields for computational drug design and materials research.. This project aims to improve the atomic interaction functions used to calculate the structural, dynamic and thermodynamic properties of molecules that alter net charge or structure in different environments. Predicting the stability of alternative protonation and tautomeric states for molecules bound to therapeutic targets is a major challenge in computational drug design. It is key to identifying the therapeutically active chemical species as well as understanding drug transport and off-target effects. The work will expand the utility of modelling software used by over 13,000 researchers worldwide. In addition, the improved interaction functions will also help in the understanding of a wide range of other materials at an atomic level.
Professor David Jamieson; Professor Dane McCamey; Professor Richard Curry Synthesis of enriched silicon for long-lived donor quantum states. We have discovered a method to make silicon highly enriched in the desirable spin-zero isotope using readily available ion implantation tools. This “semiconductor vacuum” is essential for building future quantum computer devices using the quantum spin of millions of implanted atoms with revolutionary capabilities. We have demonstrated long-lived implanted donor atom quantum states in prototype material, made possible by the depletion of background spins in natural silicon and now aim to push the enrichment to greater extremes. We will integrate the extreme material into functional devices that use electrically detected electron spin resonance to probe exceptionally durable quantum states and open a near-term pathway to large-scale devices.
Professor Ronald White; Professor Michael Brunger; Professor Mark Kushner; Dr Yang Liu Non-equilibrium presolvation electron processes at the gas-liquid interface. The interaction of low-temperature plasma electrons with liquids has served as a reducing agent in various technological applications in water treatment, agriculture, biofuels and medicine. Predictive control of the plasma-liquid interface is essential to unlocking the potential of these applications, and this has been limited by the absence of the relevant non-equilibrium transport theory describing electrons at the plasma-liquid interface together with fundamental data describing electron interactions with liquids. The project will develop a state of the art presolvation electron transport model informed by world first measurements of electron cross-sections for radicals and liquids and apply it to model plasma electrochemistry processes.

Online Seminar Announcement: Wednesday 1 December 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

Meeting URL: https://jcu.zoom.us/j/81453304396

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

Synthesis of 2D nanomaterial from waste and its application in opto-electronic and sensing

Amandeep Singh Pannu

Queensland University of Technology

The study investigates an end-to-end solution for developing carbon based 2D semiconductor nanomaterial or quantum dots from carbon rich bio-waste and demonstrates its application into thin film devices and solution based optical sensing. The presentation is divided into two parts. The first part will share the outcome of study, which explores the synthesis method to produce such high performing quantum dot material and tune its opto-electronic properties via surface engineering based on its application either in sensing or active/charge transporting layer in light emitting diodes and solar cell devices. The second part of the presentation will share the insights on how to apply this synthesized material successfully into hybrid devices.

 


Presentation
1:25 – 1:50pm

Harnessing triplet excitons in organic solid-state lasers

Atul Shukla

The University of Queensland

Organic light-emitting device technology has been shown promising for a paradigm shift from organic light-emitting diodes (OLEDs) to organic laser diodes (OLDs).[1] While significant progress has been made for organic semiconductors emitting in the blue–green region of the visible spectrum, organic laser dyes with low-energy emission (>600 nm) still suffer from high amplified spontaneous emission (ASE) thresholds and low external quantum efficiencies (EQEs) in devices under high current densities.[2, 3] In this presentation, low ASE thresholds and efficient electroluminescence (EL) from a solution-processable organic laser dye dithiophenyl diketopyrrolopyrrole (DT-DPP) will be shown. A low ASE threshold of 4 μJ cm−2 with λASE ≈ 620 nm will be presented by making constructive use of triplet excitons via doping DT-DPP in a green-emitting host matrix that exhibits thermally activated delayed fluorescence (TADF). A high EQE of 7.9% of fabricated OLEDs due to the efficient utilization of triplet excitons is demonstrated. Finally, the critical role of reverse intersystem crossing rate in achieving lasing under electrical pumping from such TADF-assisted fluorescent systems will be discussed using transient EL studies.[4]

References:
[1] A. S. D. Sandanayaka, et al., Appl. Phys. Express, 12, 061010 (2019).
[2] M. Mamada, et al., Adv. Funct. Mater., 28, 1802130 (2018).
[3] A. Shukla, et al., Adv. Opt. Mater., 8, 1901350 (2020).
[4] A. Shukla, et al., Adv. Funct. Mater., 31, 2009817 (2021).


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 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 bronson.philippa@jcu.edu.au.


Online Seminar Announcement: Wednesday 3 November 2021

Wednesday 3 November 2021

High Efficiency Deep Blue OLEDs

Jang-Joo Kim

Seoul National University, Korea
JooAm Co.

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

Meeting URL: https://jcu.zoom.us/j/83099059507

The efficiency of organic light emitting diodes has been significantly improved during the last several years by developing phosphorescent and TADF emitters with high horizontal emitting dipole orientation and high PLQY along with the development of device structure with excellent charge balance to get EQE reaching almost 40%, corresponding to almost the theoretical limit of the efficiency. The most important remaining issue is the development of deep blue OLEDs. In this talk, we will firstly present a theoretical model to analyze the degradation mechanism of OLEDs and application of the model to blue OLEDs. Then we will talk about a strategy to realize deep blue TADF OLEDs with the EQE of 28% and CIE y value of 0.09 by narrowing the emission spectrum of blue emitting TADF emitters along with high horizontal emitting dipole orientation. Lastly, we will discuss on deep blue OLEDs utilizing triplet-triplet annihilation (TTA) process based on anthracene derivatives. For blue-emitting anthracene derivatives, the theoretical maximum contribution of TTA to emissive singlet excitons is 15%, which is insufficient for high-efficiency fluorescent devices. In this study, we realised a TTA contribution of nearly 25% using an anthracene derivative, breaking the theoretical limit. As a result, efficient deep-blue TTA fluorescent devices were developed, which exhibited maximum external quantum efficiencies of 10.2%. A theoretical model will be presented to explain the experimental results considering both the TTA and RISC to a singlet state from a high level triplet state formed by the TTA process.

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 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 bronson.philippa@jcu.edu.au.


Online Seminar Announcement: Wednesday 6 October 2021

Wednesday 6 October 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

Meeting URL:https://jcu.zoom.us/j/81696511133

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

Rivers of light – ternary exciplex blends for high efficiency solution-processed red phosphorescent organic light emitting diodes

Jaber Saghaei,1 Steven M. Russell,1 Hui Jin,1 Paul L. Burn,1* Almantas Pivrikas2, Paul E. Shaw1

1Centre for Organic Photonics & Electronics (COPE), School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
2School of Engineering and Information Technology, Murdoch University, Perth, Western Australia, 6150, Australia
* p.burn2@uq.edu.au

Red-emitting organic light-emitting diodes (OLEDs) are important for displays and lighting, with the latter benefiting from solution processable materials, which would enable low embedded energy, scalable fabrication. Herein we describe the effect of annealing and phase separation on the performance of solution-processed OLEDs incorporating a light emitting layer composed of the exciplex host, m-MTDATA:OXD-7, and a red phosphorescent light-emitting dendrimer, Ir(tDCpq)3. Solution-processed OLEDs containing an annealed emissive layer with a low dendrimer concentration (2 wt%) were found to have the best performance, which was higher than the device in which the light emitting layer was not annealed. The improvement in performance of the annealed device was ascribed to improved charge mobility within the emissive layer caused by phase separation of the OXD-7. The OLEDs containing annealed m-MTDATA:OXD-7:(2 wt%) Ir(tDCpq)3 had maximum current, power and external quantum efficiencies of 17.9 cd/A, 19.4 lm/W, and 14.8±0.6%, respectively. The fact that the maximum EQE of 14.8% was larger than that expected based on the PLQY and the normal out-coupling efficiency of 20% from a bottom-emitting devices was determined to arise from the different pathways of exciton formation under photoexcitation and charge injection.

 

 


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 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 bronson.philippa@jcu.edu.au.


Online Seminar Announcement: Wednesday 1 September 2021

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

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

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.

 


Presentation
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
* p.burn2@uq.edu.au

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:

• 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 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 bronson.philippa@jcu.edu.au.


Online Seminar Announcement: Wednesday 4 August 2021

Wednesday 4 August 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/82093241646

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

Anisotropic Triplet Exciton Diffusion in Crystalline TIPS-Pentacene

Rohan J. Hudson, D.M. Huang and T.W. Kee

The University of Adelaide, Adelaide, South Australia, Australia

Singlet fission (SF) is a spin-allowed exciton multiplication process in which coupling of an excited singlet-state (S1) chromophore to an adjacent ground-state chromophore yields two triplet-state (T1) excited chromophores. This process has the potential to circumvent the theoretical efficiency limit for single-function photovoltaics, and as such has attracted significant interest in recent years. Organic SF chromophores typically exhibit significant structural anisotropy in their crystal packing, which can impact exciton transport and influence the design of SF-enhanced devices. An improved understanding of the link between structural anisotropy and exciton diffusion is therefore crucial for developing SF-based photovoltaics.
Here we use ultrafast transient absorption spectroscopy to quantify the anisotropy in the triplet exciton mobility of crystalline 6,13-(triisopropylsilylethynyl)-pentacene (TIPS-Pn), a prototypical SF chromophore. Bimolecular triplet−triplet annihilation in crystalline TIPS-Pn is well-described by a kinetic model that assumes isotropic, three-dimensional triplet exciton diffusion, but with physically unreasonable best fit parameters. Kinetic models that assume either one-dimensional or anisotropic three-dimensional exciton diffusion describe the data equally well but yield more physically realistic fit parameters, suggesting that triplet diffusion on the sub-nanosecond time scale occurs mostly along a single axis of the material. Diffusion coefficients calculated by density functional theory predict that triplet exciton diffusion occurs predominantly along the crystallographic a-axis, with migration in any other direction slower by over an order of magnitude. These findings highlight the need to treat parameters obtained from fits of experimental data with models of isotropic diffusion with caution for systems with anisotropic packing such as TIPS-Pn, and suggest that fast, directional exciton transport in layers or films of TIPS-Pn may be achieved by control of the chromophore morphology.

 

1:25 – 1:50pm

Structure-Property Relationships in Molecular Electronics

Masnun Naher,a Elena Gorenskaia,a Wenjing Hong,b Colin J. Lambert,c Richard J. Nichols,d Paul J. Low a*

a University of Western Australia, Australia;

b Xiamen University, China;

c Lancaster University, UK;

d University of Liverpool, UK

Molecular electronics (ME) is a rapidly maturing field concerned with the study of charge transport phenomena through a single molecule or an array of molecules organized between two (or more) macroscopic electrodes (Figure 1). By the careful design of the chemical structure it’s possible to study the different charge transport mechanism such as coherent tunneling and incoherent hopping and quantum interference phenomenon within the junction to achieve the functions of conventional electronic components such as chemical sensors and chemically-gated transistors (Chem-FETs), photodetectors, and thermoelectric materials.1
This presentation will describe the design and synthesis of range of linearly and cross-conjugated organic, organometallic and coordination complexes complex to study their electronic properties in the molecular junction. At the heart of this study is the exploration of the factors that influence electron transport through a molecule. In turn, this deeper understanding allows us to extend molecular design strategies beyond the search for highly conductive molecules and direct attention to more subtle concepts such as quantum interference,2 redox-gated molecular electronic response1 and the influence of the molecule-electrode contact1 and coupling to the overall electrical response of the junction (Figure 1). Molecular parameters such as the frontier orbital energy levels and HOMO-LUMO gap of the molecular candidates in their accessible redox states are therefore essential to these investigations. Therefore, in addition to the molecular junction-based measurements of molecular conductivity, investigation of the electronic structures and electrochemical properties of these molecular candidates using electrochemical, spectroelectrochemical and computational methods has also been undertaken.3

 

Figure 1: A schematic of a single-molecule junction, showing the conceptual features of the anchor group contacting to the electrode surface, a linking group or molecular backbone and some functional unit (e.g. a metal-ligand fragment).

The performance of the synthesised compounds to understand different charge transport mechanisms is being evaluated within scanning tunneling microscope break-junction (STM-BJ) in collaboration with Liverpool University (UK), and the theoretical calculations of molecular structure and model junctions were done in collaboration with Lancaster University (UK) and Xiamen University (China), and results will be reported.

References
1. M. Naher, D. C. Milan, O. A. Al-Owaedi, I. J. Planje, S. Bock, J. Hurtado-Gallego, P. Bastante, Z. M. Abd Dawood, L. Rincón-García, G. Rubio-Bollinger, S. J. Higgins, N. Agraït, C. J. Lambert, R. J. Nichols and P. J. Low, J. Am. Chem. Soc., 2021, DOI: 10.1021/jacs.0c11605.
2. F. Jiang, D. I. Trupp, N. Algethami, H. Zheng, W. He, A. Alqorashi, C. Zhu, C. Tang, R. Li, J. Liu, H. Sadeghi, J. Shi, R. Davidson, M. Korb, A. N. Sobolev, M. Naher, S. Sangtarash, P. J. Low, W. Hong and C. J. Lambert, Angew. Chem. Int. Ed., 2019, 58, 18987-18993.
3. M. Naher, S. Bock, Z. M. Langtry, K. M. O’Malley, A. N. Sobolev, B. W. Skelton, M. Korb and P. J. Low, Organometallics, 2020, 39, 4667-4687.

1:50 – 2:00pm – Questions and 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 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 bronson.philippa@jcu.edu.au.


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.


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.