Resnick Institute Seminar

Please join us!

Davoryan's talk: "Nanophotonic Platforms for Light Harvesting" 

In this talk I will give an overview of our recent studies of light-material interaction in nanoscale photonic systems. Specifically, I will discuss 1) scenarios for enhancing nonlinear quantum light emission for prospective sources of entangled light and 2) near-unity light absorption in metallic and semiconductor nanostructures for photovoltaic and photoelectrochemistry applications.

Jariwala's talk: "Ultrathin van der Waals Photovoltaics"

The isolation of stable atomically thin two-dimensional (2D) materials on arbitrary substrates has led to a revolution in solid state physics and semiconductor device research over the past decade. While, graphene is the poster child of 2D materials family, a variety of other 2D materials (including semiconductors) with varying structures and opto-electronic properties have been isolated over the last few years raising the prospects for a new class of devices assembled by van der Waals forces. A fundamental challenge in using 2D materials for opto-electronic devices is enhancing their interaction with light, ultimately responsible for higher performance and efficiency in the devices.

In this seminar, I will show our recent work on photovoltaic devices from transition metal dichalcogenides of molybdenum and tungsten (MoS₂, WSe₂ etc.). We have recently demonstrated near-unity absorption in the visible part of the electromagnetic spectrum in < 15 nm films of these semiconductors by placing them on reflecting metal substrates such as gold and silver. We have further shown that these highly absorbing, ultrathin films can be further used for fabrication of simple Schottky junction photovoltaic devices with microfabricated metallic top contacts. While, this work helps solve the light-absorption problem, the external quantum efficiency (EQE) was < 10% for our Schottky junction devices Very recently, we have extended this early work to fabricate p-n heterojunctions (p-WSe2/n-MoS2) and use graphene as a transparent top contact to amplify our current collection efficiency and push the EQE up to 50%, approaching that of many emerging photovoltaic technologies with active layers in the 100s of nm range. This represents a significant development as both light-absorption and charge collection have been addressed in these devices. Finally, I will present scope for future work using just monolayers of materials to engineer near unity light absorption and collection.