Speakers

Prof. Furong ZHU is a Professor in the Department of Physics, Associate Dean (Research and Postgraduate Studies), Faculty of Science, Director for Research Centre of Excellence for Organic Electronics, and Director for Institute of Advanced Materials at Hong Kong Baptist University (HKBU). He received his BSc and MSc in Physics from Fudan University, Shanghai China, in 1983 and 1987. He completed his Ph.D in Applied Physics at Charles Darwin University in Australia from 1990-1993. He did his post-doctoral research in the Department of Electrical and Electronic Engineering at Kyoto University in Japan from 1993-1995, and was a Research Fellow with the Department of Physics at Murdoch University in Australia from 1995-1997 working on silicon thin films derived from plasma enhanced chemical vapor deposition for device application. He joined Institute of Materials Research and Engineering (IMRE) in Singapore in 1997. Prior to HKBU, he was a Senior Scientist and a Program Manager leading the organic light-emitting diode and organic photovoltaic R&D activities at IMRE. His research interests include device physics, surface science, nanostructures and semiconducting materials-oriented research for application in organic semiconductor devices. He has graduated 15 PhD students. Currently there are 3 PhD students in his group. He has published over 200 refereed journal publications and also filed 10 patents in low processing temperature indium tin oxide (ITO) transparent electrodes and organic electronic devices. In 2019, Prof. Zhu established a start-up company, Crimson Vision Technology Limited (Crimson Vision). Crimson Vision is a technology company dedicated in developing and advancing the near-infrared (NIR) light detection techniques for fast and portable detection.

Narrowband Near-infrared Perovskite/Polymer Hybrid Photodetectors

Abstract

Solution-processable halide perovskite semiconducting materials have unique optoelectronic properties for applications in perovskite solar cells and photodetectors (PDs). The discrete perovskite PDs have a broadband photoresponse, which is sensitive over the visible wavelength range, while the polymer PDs exhibit a broadband photoresponsivity with extended absorption in the near-infrared (NIR) wavelength range, e.g., from visible light to the NIR wavelength of >1100 nm. The visible-blind NIR photodetection with these broadband PDs requires the use of the filters or the specially designed photonic structures for achieving the photodetection over a well-defined wavelength range. However, the rigidity of the filters and the difficulty of assembling small-size optical units containing them present technical limitations. Incorporation of a bandpass filter also reduces the overall radiometric performance of the photodetectors, which increases the cost and complexity of its device integration.

Different narrowband photodetection approaches have been attempted, e.g., incorporating a microcavity structure and using charge collection narrowing (CCN) effect in the PDs. In the CCN-type PDs, a relatively thick photoactive layer, e.g., > 2500 nm thick photoactive layer, is adopted to reduce the collection efficiency of the charge carriers generated by the visible light absorbed near the upper region of a thick photoactive layer. The use of a thick active photoactive layer in a CCN-type PD faces some technical challenges: (1) The responsivity of the CCN-type PDs is limited as a large amount of the incident light is attenuated by the thick photoactive layer. (2) Perovskite PDs with a thick photoactive layer often associates with a slower response speed due to the decrease in its carrier transit time limited cut-off frequency. (3) The photodetection spectrum in the CCN-type PDs is limited by the absorption edge of the photoactive layer. This talk discusses a novel hybrid PD with a heterostructure perovskite/polymer photoactive layer for alleviating the challenges: (1) to achieve high hole transport efficiency by incorporating a thinner perovskite, (2) to realize narrowband NIR detection through buildup of the space charges at the perovskite/polymer interface, and (3) to improve the device design freedom by incorporating different combinations of perovskite charge transporting layer and the NIR absorbing layer in the perovskite/polymer structure. The hybrid PDs with a thinner photoactive layer results in an obvious increase in the responsivity and response speed. The hybrid PDs thus demonstrated have a narrowband NIR detection and a -3 dB cut-off frequency of 300 kHz, offering an exciting option for a plethora of applications in bio-imaging, environmental detection, and security monitoring.