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.