Publications associated with Semiconductor Materials, Devices & Nanostructures

The entangled triplet pair state in acene and heteroacene materials.

Nature communications 8 (2017) 15953-

CK Yong, AJ Musser, SL Bayliss, S Lukman, H Tamura, O Bubnova, RK Hallani, A Meneau, R Resel, M Maruyama, S Hotta, LM Herz, D Beljonne, JE Anthony, J Clark, H Sirringhaus

Entanglement of states is one of the most surprising and counter-intuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which mediates the spin-conserving fission of one spin-0 singlet exciton into two spin-1 triplet excitons. Despite long theoretical and experimental exploration, the nature of the triplet-pair state and inter-triplet interactions have proved elusive. Here we use a range of organic semiconductors that undergo singlet exciton fission to reveal the photophysical properties of entangled triplet-pair states. We find that the triplet pair is bound with respect to free triplets with an energy that is largely material independent (∼30 meV). During its lifetime, the component triplets behave cooperatively as a singlet and emit light through a Herzberg-Teller-type mechanism, resulting in vibronically structured photoluminescence. In photovoltaic blends, charge transfer can occur from the bound triplet pairs with >100% photon-to-charge conversion efficiency.

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