Boosting internal quantum efficiency via ultrafast triplet transfer to 2H-MoTe2 film.

ABSTRACT

Organic systems often allow to create two triplet spin states (triplet excitons) by converting an initially excited singlet spin state (a singlet exciton). An ideally designed organic/inorganic heterostructure could reach the photovoltaic energy harvest over the Shockley-Queisser (S-Q) limit because of the efficient conversion of triplet excitons into charge carriers. Here, we demonstrate the molybdenum ditelluride (MoTe2)/pentacene heterostructure to boost the carrier density via efficient triplet transfer from pentacene to MoTe2 using ultrafast transient absorption spectroscopy. We observe carrier multiplication by nearly four times by doubling carriers in MoTe2 via the inverse Auger process and subsequently doubling carriers via triplet extraction from pentacene. We also verify efficient energy conversion by doubling the photocurrent in the MoTe2/pentacene film. This puts a step forward to enhancing photovoltaic conversion efficiency beyond the S-Q limit in the organic/inorganic heterostructures.