2D Heterostructures for Energy Storage and Electronics: Exploring the Limits of Weak and Strong Interlayer Interactions

Scott C. Warren, Ph.D.

The ability to alter distances between atoms is among the most important tools in materials design.  Despite this importance, controlling the interlayer distance in stacks of 2D materials remains a challenge.  This talk will present two strategies for controlling this distance, thereby giving rise to several fascinating new classes of materials for electronics and energy storage.

In the first strategy, we self-assemble a monolayer of organic molecules between monolayers of a 2D semiconductor such as MoS₂ or phosphorene.  The resulting 3D materials are crystalline and have an increased interlayer distance, which gives rise to fascinating and unusual electronic properties.  We demonstrate a 3D hybrid made from monolayer MoS₂ and organic molecules that retains the desirable properties of monolayer MoS₂, such as strong photoluminescence.  Even more surprising is that these materials are relatively conductive—thereby allowing the desirable properties of 2D materials to be harnessed in a 3D format that is suitable for electronic devices.

The second strategy introduces a new pathway to reduce interlayer distance.  We utilize “2D electrenes,” a new 2D material with an electrical conductivity that rivals silver (JACS 138, 16089 (2016)).  2D electrenes have radically different electronic structures: they have planes of electrons that are physically separated from planes of cations.   Using DFT calculations and preliminary experiments, we show that electrenes act as electron donors to 2D metals, semiconductors, and insulators.   These materials are the 2D analogs of donor-acceptor systems and have interlayer distances that approach those of covalent or ionic materials.  I will describe these structures and their fascinating properties, as well as their role in battery electrodes.

Scott studied chemistry at Whitman College from 1998 to 2002 and conducted solar energy research at the National Renewable Energy Laboratory during the summers. He earned his Ph.D. in 2007 with work on the self-assembly of fuel cell electrodes in the groups of Uli Wiesner and Frank DiSalvo at Cornell. He was a post-doctoral fellow with Michael Graetzel at EPFL, Switzerland, from 2007 to 2010. During that time, he directed a European consortium on water splitting and was a visiting researcher at the Technion-Israel Institute of Technology with Avner Rothschild. Scott returned to the U.S. in 2011, working on nanoparticle electronics at Northwestern University with Bartosz Grzybowski. He has been an assistant professor in the departments of chemistry and applied physical sciences at UNC Chapel Hill since 2013.  He has received the Beckman Young Investigator Award and selected as a Research Corp Scialog Fellow.