Mar. 10th, 2025 Seminar Speech

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Created on Monday, 03 March 2025 16:21

Last Updated on Monday, 03 March 2025 16:25

Published on Monday, 03 March 2025 16:25

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Speaker: Dr. Le Yang

Topic: Triplet-triplet annihilation strategies in photon-upconversion & OLEDs

Location: Room 102, Boya Lecture Building

Time: Mar. 10th, 2025 10:20-12:10 AM

Abstract:

Triplet-triplet annihilation (TTA) enables efficient and versatile photon-upconversion in organics. The same process also can enhance OLED efficiencies by utilising dark triplets.^1-4 Here, we present progresses on efficient TTA-UC in novel composite systems^5-6:

First, we use a hybrid nanocrystal as triplet-sensitizer, and two different organic upconversion emitters, we observe for the first time, a multi-fold enhancement in the upconversion efficiency in such a composite hybrid system.⁵

Next, solid-state photon-upconversion always suffers from low efficiencies and high threshold excitation power. We showcase a novel composite-sensitizer, inspired by the BHJ donor-acceptor of organic photovoltaics, for TTA-UC devices, leading to highly-efficient solid-state upconversion devices with low excitation power, through a one-step solution method. We also scaled-up this strategy on highly-flexible large-area substrates.⁶

Lastly, we explore overcoming the efficiency bottleneck in simple fluorescent OLEDs. First, in a dual-dopant system, lifting rubrene-derivative-based OLEDs to >20% EQE.^1-2 Secondly, in single-dopant devices, by triplet-fusion mechanism, drawing parallels to TTA-UC, to enhance device efficiency ceiling.^3-4

1. L Yang et al, Joule 2019, 3, 2381–2389.
2. D Di, AS Romanov, L Yang et al Science, 2017, 356, 159–163.
3. L Yang et al. Nanoscale Adv. 2022, 4, 1318-1323.
4. D Di, L Yang et al, Adv. Mater. 2017, 29, 1605987.
5. XW Chua, L Dai, M Anaya, SD Stranks, L Yang et al, ACS Nano 2024, 18, 23, 15229–15238.
6. P Bi, L Yang et al, Nature Communications 2024, 15 (1), 5719.

About the Speaker: 

Service Unit: National University of Singapore

Title: Adjunct Assistant Professor

Education and Research Experience:

Dr Le Yang received her PhD from the University of Cambridge, where she and her colleagues discovered a new emission mechanism in a class of then-new materials, leading to a breakthrough and record-efficiency organic LEDs, useful for next-generation display technology. Le is now working in IMRE, on luminescent materials, optoelectronics and biosensors, leading the “PROFESS” Group (Printed Organic Flexible Electronics & Sensors). She is also the Head of Department (Sensors & Flexible Electronics). Her notable work has been published in Science, Nature Materials, Nature Communications, Joule, etc; and her team has produced numerous IPs/patents. Le is active in the ecosystem, eg being Associate Editor of Materials Today Chemistry, Joint-Secretary executive committee of the Materials Research Society-Singapore, chairing several conferences and leading outreach activities.

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