Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals

Publication Type:

Journal Article

Source:

Nat. Mater., nature.com, Volume 13, Issue 11, p.1039-1043 (2014)

ISBN:

1476-1122

Keywords:

2014

Abstract:

Triplet excitons are ubiquitous in organic optoelectronics, but they are often an undesirable energy sink because they are spin-forbidden from
emitting light and their high binding energy hinders the generation of
free electron-hole pairs. Harvesting their energy is consequently an
important technological challenge. Here, we demonstrate direct excitonic
energy transfer from 'dark' triplets in the organic semiconductor
tetracene to colloidal PbS nanocrystals, thereby successfully harnessing
molecular triplet excitons in the near infrared. Steady-state excitation
spectra, supported by transient photoluminescence studies, demonstrate
that the transfer efficiency is at least (90 ± 13)%. The mechanism is a
Dexter hopping process consisting of the simultaneous exchange of two
electrons. Triplet exciton transfer to nanocrystals is expected to be
broadly applicable in solar and near-infrared light-emitting applications,
where effective molecular phosphors are lacking at present. In particular,
this route to 'brighten' low-energy molecular triplet excitons may permit
singlet exciton fission sensitization of conventional silicon solar cells.