Date| 19 September 2019 (Tuesday)
Venue| 2.304 Think Tank 19, Building 2 Level 3
Time| 1400 – 1430
Title| Designing Polymeric Mixed Conductors for High Performance Bioelectronics and Wearable Electronics
Speaker| Assistant Professor Leong Wei Lin, School of Electrical and Electronic Engineering, NTU.
Time| 1430 – 1500
Title| Solution Processed Halide Perovskites and Oxide Semiconductors for Solar Cells, Lighting and Electronics
Speaker| Associate Professor Nripan Mathews, School of Materials Science and Engineering, Energy Research Institute, NTU.
|Designing Polymeric Mixed Conductors for High Performance Bioelectronics and Wearable Electronics||Solution Processed Halide Perovskites and Oxide Semiconductors for Solar Cells, Lighting and Electronics|
Organic electrochemical transistors (OECTs) are highly attractive for applications ranging from circuit elements, neuromorphic devices to transducers for biological sensing and the archetypal channel material is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS. The operation of OECTs involves the doping and de-doping of a conjugated polymer due to ion intercalation under the application of a gate voltage. However, the challenge is the trade-off in morphology for mixed conduction since good electronic charge transport requires a high degree of ordering among PEDOT chains, while efficient ion uptake and volumetric doping necessitates open and loose packing of the polymer chains. Here we demonstrate ionic liquid doped PEDOT:PSS that overcomes this limitation. Ionic liquid doped OECTs show high transconductance, fast transient response and high device stability over 3600 switching cycles. The OECTs are further capable of having good ion-sensitivity. We also look at strategies to achieve polymer films which are robust towards physical deformation and able to self-heal without compromising electronic properties as well as deposition routes for making devices on unconventional curved substrates. These findings pave the way for higher performance bioelectronics and flexible/wearable electronics.
In this talk, I will provide an introduction to halide perovskites which are solution processable semiconductors that have found applications in solar cells. The efficiencies in these devices are now close to that of silicon solar cells, despite its solution processability. This is attributable to the defect tolerant nature of the perovskite material as well as the good optical absorption as well as the long electron, hole carrier diffusion lengths. Our group’s recent research in this area would be covered, with the view of increasing its stability as well as scaling the size of the solar cells to 30cmX30cm sizes. The use of halide perovskite systems in light emitting diodes would also be briefly discussed. Finally, our group’s efforts in solution processed oxide semiconductors for thin film transistors and neuromorphic devices would be presented.
|ABOUT THE SPEAKER
Dr. Leong is an Assistant Professor at Nanyang Technological University (NTU), School of Electrical and Electronic Engineering (EEE). She performed her postdoctoral fellowship under Nobel Laureate Professor Alan Heeger in University of California, Santa Barbara (UCSB), working on polymer and small molecule solar cells, where she was part of the team to achieve world record efficiency. In 2012, she joined Institute of Materials Research and Engineering (IMRE), working in the area of printed electronics and photovoltaics. Her research focuses primarily on electronic materials (organic and hybrid) for solar energy conversion, field-effect transistors, memory devices and chemical sensors.
|ABOUT THE SPEAKER
Dr. Nripan Mathews holds the position of Provost’s chair in Materials Science and Engineering at NTU. He is an Associate Professor at the School of Materials Science and Engineering and the Energy Research Institute@ NTU (ERIAN). His primary interests are on the electronic and optical properties of solution processed materials and how they can be adapted for practical applications. His primary research interests are photovoltaics, field effect transistors and light emitting diodes.