FoS won Young Researcher Award

24 Apr 2015 The Young Researcher Award this year was won by Prof Goki EDA from the Department of Physics for his research area at the nanoscale showing a unique set of distinct behaviours.

His team is particularly interested in how atomically thin “two-dimensional (2D)” materials interact with light. Motivated by the fact that graphene, the archetypal 2D material, absorbs light efficiently despite being only one-atom-thick, his team set out to investigate light-matter interaction in other 2D systems. They found that another family of 2D materials called layered transition metal dichalcogenides exhibits unusual optical absorption and that a single layer of MoS₂ having a thickness of less than one nanometre absorbs more than 30% of incident light. With careful photoluminescence studies, they have showed that this strong light-matter interaction is due to an effect called band nesting and is uniquely seen in a specific group of 2D materials.

The main challenge was collecting convincing evidence that the strong absorption comes from the band nesting effect. This required careful measurements of often very weak photoluminescence signals. A series of time consuming measurements yielded data that finally led them to the conclusion.

Strong light absorption is a fundamental requirement for realizing any optoelectronic devices such as solar cells and photodetectors. Conventional devices are rather bulky because the light absorbing layer needs to be sufficiently thick to effectively harness the energy of light. Silicon-based solar cells are rigid and bulky for this reason. Their findings suggest that they can use 2D materials to realize light weight, ultrathin optoelectronic devices that can be rolled up like a piece of paper.

In order to translate strong light absorption to implementation of proactively devices, one needs to better understand a number of things related to the relaxation of photo-excited electrons and holes. Therefore the group of Prof Eda continues to study the dynamics of excited states in 2D systems and ways to manipulate them.

Image shows a dynamics of excited states in 2D systems.