From power generation to quantum information science - material development for enhanced singlet fission

 

Singlet fission is a bi- (or multi- )molecular exciton multiplication process, where one singlet exciton is converted to two triplet excitons of roughly half the energy. For this process to take place, a molecular system must possess (1) appropriate triplet energies relative to the singlet, which is a common property of acenes larger than anthracene, and (2) sufficient intermolecular electronic coupling for Dexter energy transfer to be possible.  Fifteen years ago, our focus was the utilization of this process to enhance the power conversion efficiency of silicon photovoltaics, as a method to break the Shockley-Queisser limit.  This approach requires the correlated triplet state to dissociate into free triplets, which can then be individually harvested for photocurrent generation. More recently, in collaboration with researchers at NREL, we became interested in a different application: By completely re-designing molecular architectures to prevent the triplets from dissociating, systems were developed where the longer-lived triplet pair converted to a correlated quintet state, which can be addressed by microwave irradiation and read-out optically. This talk will cover material design for both applications, along with our current design goals for qubits with µs coherence at room temperature.