演講/活動

2019-12-17 10:42:00陳秋雲(2019.12.24 Talk) Excitonic Materials for Optoelectronic Applications

#WELCOME ALL TO COME

Time:Dec. 24, 2019 Tuesday 15:30—17:00PM
Venue:R108, 1F Engineering Building 4, NCTU
交通大學工程四館一樓108室(知新廳)

Speaker:Dr. Der-Hsien (Danny) Lien 連德軒 博士
Postdoctoral Fellow at EECS, University of California, Berkeley, USA

Language: English

Abstract
Once semiconductors are thinned down to the atomic level, strong many-body interactions cause new physics to emerge that deviates from well-known free carrier models. A prominent effect is that carriers turn from “free” to “bound” species even at room temperature, so-called room temperature excitons. Using monolayer semiconductors as the platform (i.e., semiconductors at their ultimate thickness limits), I will show that such thickness-determined excitonic systems are promising for optoelectronic applications due to their near-unity photoluminescence (PL) quantum yields (QYs) [1], a key figure of merit dictating the maximum efficiency achievable in light-emitting diodes, lasers and solar cells. I will discuss the comprehensive recombination mechanisms of 2D excitons in monolayers and showed that the non-radiative recombination pathways could be fully suppressed by electrostatic gating, despite the presence of native defects [2]. This research reveals that room-temperature excitons are robust and bright regardless of monolayer quality, indicating the potential of achieving highly efficient excitonic devices. To deal with the injection inefficiency caused by Schottky contacts, I will show an AC carrier injection architecture, a device concept that is capable of efficiently injecting carriers in various excitonic systems, including monolayer semiconductors, with demonstrations of bright light-emitting devices from infrared to ultraviolet regimes [3].
[1] Science 2015, 350, 1065.
[2] Science 2019, 364, 468–471.
[3] Nature Commun. 2018, 9, 1129.