Ultrafast exciton dissociation and long-lived charge separation in a photovoltaic pentacene-MoS2 van der Waals heterojunction

Stephanie Bettis Homan, Vinod K. Sangwan, Itamar Balla, Hadallia Bergeron, Emily A Weiss, Mark C Hersam

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

Van der Waals heterojunctions between two-dimensional (2D) layered materials and nanomaterials of different dimensions present unique opportunities for gate-tunable optoelectronic devices. Mixed-dimensional p-n heterojunction diodes, such as p-type pentacene (0D) and n-type monolayer MoS2 (2D), are especially interesting for photovoltaic applications where the absorption cross-section and charge transfer processes can be tailored by rational selection from the vast library of organic molecules and 2D materials. Here, we study the kinetics of excited carriers in pentacene-MoS2 p-n type-II heterojunctions by transient absorption spectroscopy. These measurements show that the dissociation of MoS2 excitons occurs by hole transfer to pentacene on the time scale of 6.7 ps. In addition, the charge-separated state lives for 5.1 ns, up to an order of magnitude longer than the recombination lifetimes from previously reported 2D material heterojunctions. By studying the fractional amplitudes of the MoS2 decay processes, the hole transfer yield from MoS2 to pentacene is found to be ∼50%, with the remaining holes undergoing trapping due to surface defects. Overall, the ultrafast charge transfer and long-lived charge-separated state in pentacene-MoS2 p-n heterojunctions suggest significant promise for mixed-dimensional van der Waals heterostructures in photovoltaics, photodetectors, and related optoelectronic technologies.

Original languageEnglish
Pages (from-to)164-169
Number of pages6
JournalNano Letters
Volume17
Issue number1
DOIs
Publication statusPublished - 2017

Fingerprint

polarization (charge separation)
Excitons
Heterojunctions
heterojunctions
excitons
dissociation
Optoelectronic devices
charge transfer
Charge transfer
surface defects
optoelectronic devices
absorption cross sections
Surface defects
photometers
Photodetectors
Absorption spectroscopy
absorption spectroscopy
Nanostructured materials
trapping
diodes

Keywords

  • Charge transfer
  • Organic
  • Transient absorption spectroscopy
  • Transition metal dichalcogenide
  • Ultrafast

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

Cite this

Ultrafast exciton dissociation and long-lived charge separation in a photovoltaic pentacene-MoS2 van der Waals heterojunction. / Homan, Stephanie Bettis; Sangwan, Vinod K.; Balla, Itamar; Bergeron, Hadallia; Weiss, Emily A; Hersam, Mark C.

In: Nano Letters, Vol. 17, No. 1, 2017, p. 164-169.

Research output: Contribution to journalArticle

Homan, Stephanie Bettis ; Sangwan, Vinod K. ; Balla, Itamar ; Bergeron, Hadallia ; Weiss, Emily A ; Hersam, Mark C. / Ultrafast exciton dissociation and long-lived charge separation in a photovoltaic pentacene-MoS2 van der Waals heterojunction. In: Nano Letters. 2017 ; Vol. 17, No. 1. pp. 164-169.
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