Two-dimensional (2D) materials have emerged as a promising material system for electronica and optoelectronic applications. In this talk, I will present our recent advancements in improving material quality as well as developing light-emitting devices of the monolayer chalcogenides. We have developed a defect passivation technique that enables the monolayer MoS2 to achieve near-unity quantum yield. The work presents the first demonstration of an optoelectronically perfect monolayer. Moving forward to the device development, forming electron and hole selected contacts is a necessary step for a light-emitting device but is challenging for 2D monolayers. We circumvent this challenge via a new device design that allows for high-level injection of electrons and holes without the requirement of ohmic contacts. Taking advantage of the device simplicity, we are able to show the first millimeter-scale light emission and transparent digital display using 2D monolayers. Additionally, I will discuss the challenges of the materials system and possible solutions towards high efficient monolayer light-emitting devices.
Der-Hsien (Danny) Lien is a Postdoctoral Fellow at University of California, Berkeley. He received his Ph.D. degree in Electrical Engineering from National Taiwan University in 2015. His research interests lie in the fields of materials physics and electronic engineering. His current research focuses on the physics of nanoscale electronic materials and their optoelectronic applications. He has actively performed research in several other disciplines including printable electronics, ultrasonic thermal imaging, and energy harvesting. His first-authored papers are widely cited and have appeared in many leading academic journals and conference, including Science, Nature Communications, and Symposia on VLSI Technology, etc. He has won the Gold Medalist Award in Green Tech Contest in 2014 hold by TECO TECHNOLOGY for the originality and innovation of his research. He was recognized for the contributions to the Electronic Device Society and awarded the IEEE EDS PhD Student Fellowship in 2015.