Cottrell Scholar Awards - 2017
Simulating the Effects of Nanoscale Disorder on Energy Transport in Molecular Semiconductors
Organic molecular semiconductors (OMS) are electronically active plastics that are increasingly used in applications ranging from efficient lighting to solar energy technologies. This growing class of materials offers an inexpensive, mechanically and electronically tunable alternative to traditional crystalline semiconductors such as silicon.
Adam P. Willard, chemistry, Massachusetts Institute of Technology, has received a Cottrell Scholar Award from Research Corporation for Science Advancement to develop a theoretical method to tackle the difficulties of investigating the charge and energy transport properties of disordered molecular semiconductors.
“The emergent electronic properties of OMS are highly sensitive to how molecules are arranged within the material,” Willard notes. “We do not yet understand how to quantify this morphology dependent contribution to the macroscopic electronic properties of these materials,” a shortcoming that has significantly hindered their development.
Willard said his approach will be to develop a theoretical method for simulating exciton dynamics in the presence of nanoscale molecular disorder. Coulombically bound excited electronhole pairs, excitons are the currency of molecular-scale electronic energy transfer in many systems ranging from photosynthetic light-harvesting devices to ultra-efficient solid-state lighting. Understanding how the macroscopic properties of semiconducting materials emerge from the microscopic dynamics of excitons has been a problem of long-standing scientific interest.
“We apply our theoretical method to study how exciton properties are shaped by nanoscale molecular morphology and how the presence of molecular disorder can drive exciton dissociation into free charge carriers,” Willard said.
Basically, Willard intends to take a two-pronged approach, developing a theoretical framework combining classical models of nanoscale disorder and coarse-grained model quantum dynamics to overcome the system size limitations of nanoscale molecular disorder and the lack of molecular resolution in the quantum-dynamics model.
“In this approach we simulate the same system with two separate yet co-evolving models,” he said.
An efficient theoretical method capable of quantifying the emergent electronic effects of molecular morphology would enable the development of the new generation of flexible semiconductors with novel and customizable electronic properties.
There is also an education component to the Cottrell Scholar Award. Willard intends to apply some of the funding to enhance learning outcomes for core concepts in molecular physics. “Our approach uses the development of two new simulation modules,” he said. “The first module provides a virtual framework to design and carry out experiments on nanoscale systems. The second module applies data-derived audio output to standard molecular visualization techniques.” These modules will be incorporated into the physical chemistry curriculum at MIT, he added.