4.8 Article

Ultrafast Exciton Dissociation and Long-Lived Charge Separation in a Photovoltaic Pentacene-MoS2 van der Waals Heterojunction

期刊

NANO LETTERS
卷 17, 期 1, 页码 164-169

出版社

AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b03704

关键词

Organic; transition metal dichalcogenide; transient absorption spectroscopy; ultrafast; charge transfer

资金

  1. Materials Research Science and Engineering Center (MRSEC) of Northwestern University [NSF DMR-1121262]
  2. 2-DARE program [NSF EFRI-1433510]
  3. National Institute of Standards and Technology (NIST) [CHiMaD 70NANB14H012]
  4. Argonne-Northwestern Solar Energy Research (ANSER) Energy Frontier Research Center [DOE DE-SC0001059]
  5. NSERC Postgraduate Scholarship-Doctoral Program
  6. Directorate For Engineering
  7. Emerging Frontiers & Multidisciplinary Activities [1433510] Funding Source: National Science Foundation

向作者/读者索取更多资源

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 (OD) 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 similar to 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.

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