8:45 AM - 8:50 AM: Welcome and Opening Remarks
Zakya H. Kafafi, Lehigh Univ. (United States); Ifor D. W. Samuel, Univ. of St. Andrews (United Kingdom); Thuc-Quyen Nguyen, Univ. of California, Santa Barbara (United States)

8:50 AM - 9:20 AM:
Breaking the lifetime barrier for deep blue phosphorescent OLEDs

Stephen R. Forrest Univ. of Michigan (United States)

Perhaps the single most important problem confronting the development of OLED displays and lighting today is how to achieve sufficiently long triplet-controlled emission device lifetime to prevent rapid color change during operation, while achieving 100% internal emission efficiency. It has been shown¹ that bimolecular (e.g. triplet-polaron, triplet-triplet) annihilation provides a source of energy sufficient to destroy the blue triplet chromophore (whether a phosphor or a TADF molecule) or its host. Since that time, many materials, structures and strategies to extend blue emission lifetime based on this understanding have been demonstrated. Furthermore, various molecular fragments have been identified whose presence leads to the observed luminance loss. Unfortunately, a fully satisfactory solution has not been shown where blue triplet emitter lifetime is sufficient to meet the standards of high performance displays, although white OLED illumination sources may now have adequate lifetime to meet industry standards. In this talk I will discuss progress in extending blue phosphorescent OLED (PHOLED) lifetime, and in understanding of the limitations to extending the lifetime of blue triplet emitters. In particular, I will focus on the relationship between radiative state lifetime, exciton density, and the longevity of the PHOLED. I will review efforts that have resulted in increasing the deep blue phosphorescent longevity by at least 14 X via emitter design, polaritons, and optical cavity engineering. Prospects for future advances will be discussed.

1. “Intrinsic luminance loss in phosphorescent small-molecule organic light emitting devices due to bimolecular annihilation reactions”. N.C. Giebink, B.W. D’Andrade, M.S. Weaver, P.B. Mackenzie, J.J. Brown, M.E. Thompson, and S.R. Forrest, J. Appl. Phys., 103, 044509 (2008).

Stephen R. Forrest is a Professor of Electrical Engineering, Physics and Materials Science and Engineering at the University of Michigan. He and his group conduct research on photovoltaic cells, organic light emitting diodes, and lasers & optics. His investigations have resulted in five startup companies, 385 issued patents, and key technologies that are pervasive in the marketplace. He has graduated 69 Ph.D. students and his first book, Organic Electronics: Foundations to applications, was published in September 2020, by Oxford University Press.

9:20 AM - 9:25 AM: Q&A with Stephen R. Forrest

9:25 AM - 9:55 AM:
Impurity conundrum of ultralong organic phosphorescence

Bin Liu National Univ. of Singapore (Singapore)

Commercial carbazole (Cz) has been widely used to synthesize organic functional materials, which are entwined with recent breakthroughs in ultralong organic phosphorescence, thermally activated delayed fluorescence, organic luminescent radicals, and organic semiconductor lasers. Recently, we discovered that different from commercial Cz, the fluorescence of lab-synthesized-Cz (Lab-Cz) is blue-shifted by 54 nm and the well-known room-temperature ultralong phosphorescence almost disappears. Detailed studies reveal the presence of a Cz isomer as the impurity, which is widespread in commercial Cz sources with <0.5 mol%. Ten representative Cz derivatives were resynthesized from the Lab-Cz and all failed to show the reported ultralong phosphorescence in the same crystal states. However, even 0.1 mol% isomer doping can recover the reported ultralong phosphorescence. The presence of the isomer in commercial carbazole triggers us to re-examine the structure-property of many optically active materials with important discoveries.

Professor Bin Liu is Tan Chin Tuan Centennial Professor at the National University of Singapore (NUS). Bin graduated with a bachelor’s degree from Nanjing University and a Ph.D. in Chemistry from NUS. She had postdoctoral training at the University of California, Santa Barbara before joining NUS in 2005. Bin has been well-recognized for her contributions to polymer chemistry and organic nanomaterials for energy and biomedical applications.

9:55 AM - 10:00 AM: Q&A with Bin Liu

Coffee Break 10:00 AM - 10:30 AM

10:30 AM - 11:00 AM:
Detecting the invisible: fluorescence-based identification of chemical threats

Paul Burn The Univ. of Queensland (Australia)

Fluorescence-based sensing has the potential for sensitive (trace), rapid and selective detection of chemical threats and is compatible with low power portable detectors that can be used in the field by military personnel, first responders, healthcare workers and those tasked with environmental monitoring. Chemical threats can include illicit drugs, toxic industrial chemicals, pesticides improvised explosive devices, and chemical warfare agents. This presentation will use practical examples to introduce different modes of fluorescence sensing, illustrate the key issues relating to solid-state detection of chemical vapours, and multivariate strategies to achieve selective chemical threat detection.

Professor Paul Burn FAA FRACI FRSC is Director of the Centre for Organic Photonics & Electronics and a UQ Laureate Fellow at The University of Queensland, Australia. His research focuses on the development and application of organic semiconductor materials.

11:00 AM - 11:05 AM: Q&A with Paul Burn

11:05 AM - 11:35 AM:
Molecular electronic materials and devices for solar energy conversion

Jenny Nelson Imperial College London (United Kingdom)

Solar radiation will be the largest single source of electricity in a low-carbon future. To maximise the potential of solar power, new materials will be needed to harvest and convert solar energy alongside existing photovoltaic technologies. Molecular electronic materials, such as conjugated polymers and molecules, can achieve photovoltaic conversion through a process of photon absorption, charge separation and charge collection. The materials are appealing because of the potential to tune their properties through chemical design and their compatibility with high-throughput manufacture. They are also interesting model systems for photochemical energy conversion because of their parallels with natural photosynthesis. Through a remarkable series of advances in materials design, the efficiency of photovoltaic energy conversion in molecular materials has risen from 1% to around 20% within two decades, surpassing most predictions. We will discuss the factors that control the function of molecular solar cells including the nature of the charge separating heterojunction, and the impact of chemical and physical structure on phase behaviour, energy and charge transport, light harvesting, and loss pathways. Finally, we will address the limits to conversion efficiency in such systems.

Jenny Nelson is a Royal Society Research Professor at Imperial College London, where she researches novel materials for solar energy conversion. Her current research is focused on understanding structure-property relationships in molecular and hybrid semiconductor materials and how these relationships influence the mechanisms of solar energy conversion. She also works on the role of renewable energy technologies in mitigating climate change. She holds several awards including the 2016 Institute of Physics Faraday medal and the 2023 IEEE PVSC Cherry Award and was elected as a Fellow of the Royal Society in 2014.

11:35 AM - 11:40 AM: Q&A with Jenny Nelson

Event Details

FORMAT: General session with live audience Q&A to follow presentations.
MENU: Coffee, decaf, and tea will be available outside the presentation room.
SETUP: Theater style seating.