Dr. R. K. Kathir

Spin mixing in intra-molecular singlet fission

Singlet fission (SF) is a photophysical phenomenon that can lead to the production of multiple charge carriers from a single photo excitation [1]. Predominantly observed in organic molecules, it has gained widespread interest in the past decade due to its possibility to surpass the Shockley-Queisser limit of solar cell power conversion efficiency. Recent studies have shown that the spin-spin interactions between electronic states of the molecule plays a significant role in determining the yield of free charge carriers in SF [2,3]. Results from electron spin resonance (ESR) experiments show a considerable mixing between quintet and singlet spin manifolds of the multiexcitonic |1(T T ) state in SF, an observation that was previously ignored in all but few models of the SF process.

In our project, we theoretically model the dynamics of the spin-mixed states triplet in SF using ab-initio electronic structure theory and semi-classical dynamics methods. The results from the project will help in gaining a more nuanced understanding of the SF process. This work is carried out in the group of Prof. Michael Thoss in collaboration with Dr. Pedro B. Coto, of the Materials
Physics Center in San Sebastian.

References:

[1] M. Smith, and J. Michl, Chem. Rev., 2010, 110, 68916936.
[2] L. Weiss et al, Nat. Phys., 2017, 13.2, 176181.
[3] M. Tayebjee et al, Nat. Phys., 2017, 13.2, 182-188