Resnick Institute


Singlet Fission: Understanding Mechanisms and Designing Molecules

Organic solar cells offer an environmentally friendly and inexpensive alternative to their inorganic counterparts, but to-date their applications have been limited by relatively low efficiencies. Recently, Singlet Fission (SF) has emerged as a particularly promising route to high-efficiency organic photovoltaics, however the lack of a fundamental understanding of the process and the small number of chromophores that exhibit this property have hindered progress.

In this talk, we present our theoretical investigations into the detailed mechanisms of SF that yield a priori design principles for novel organic chromophores. SF is a phenomenon where a single exciton created by photon absorption spontaneously splits into two long-lived triplet excitons that may undergo independent charge separation at a donor-acceptor interface.

We employ a combination of electronic structure calculations and quantum dynamic simulations to uncover two distinct pathways for SF in non-bonded and covalently bonded pentacene dimers. In each case, we identify the underlying energetics, vibronic couplings, and the intra- and inter-molecular interactions that may be used to tune SF rates. Furthermore, using novel orbital analyses, we uncover correlations between bonding topology and enhanced visible light absorption in acene-based molecules.

Combining the insights from these studies, we generate design principles for next-generation organic chromophores, and working with experimental collaborators we verify them.

About Nandini

Nandini Ananth is an Assistant Professor in the Department of Chemistry and Chemical Biology at Cornell University. She obtained her Bachelors in Chemistry from Stella Maris College, Chennai followed by a Masters from the Indian Institute of Technology at Madras.

Her undergraduate research included implementing logic gates for quantum computing using Nuclear Magnetic Resonance and Semiclassical Dynamics. She obtained her Ph.D. developing Semiclassical methods for quantum dynamic simulations in complex systems working with William Miller at the University of California, Berkeley.

After graduation, she accepted a position as postdoctoral scholar in Thomas Miller's group at Caltech where her research focused on developing path-integral methods for the simulation of electronically nonadiabatic processes in the condensed phase.

Since beginning at Cornell in 2012, her research has focused on developing and using techniques based on semiclassical theory and the path integral formulation of quantum mechanics to simulate charge and energy transfer processes in complex chemical systems. Target applications involve designing novel materials relevant to renewable energy technologies including organic photovoltaics and transition metal complexes for photocatalytic water splitting.

During her time at Cornell she has received several awards including the GPSA Faculty Mentor Award, Cottrell Scholar Award, the Sloan Foundation Research Fellowship, NSF CAREER Award, NSF EAGER Award, and the Army Research Office Young Investigator Award.