title: Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals.
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.
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Thompson
authors.affiliation: 1] Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Mark W B
authors.initials: MW
authors.lastname: Wilson
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Congreve
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Brown
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Scherer
authors.affiliation: 1] Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Bischof
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Mengfei
authors.initials: M
authors.lastname: Wu
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Nadav
authors.initials: N
authors.lastname: Geva
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Welborn
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Troy Van
authors.initials: TV
authors.lastname: Voorhis
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bulović
authors.affiliation: 1] Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Moungi G
authors.initials: MG
authors.lastname: Bawendi
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Baldo