Journal
NANO LETTERS
Volume 17, Issue 5, Pages 3176-3181Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b00695
Keywords
Transition metal dichalcogenide; organic-inorganic heterojunction; hybrid charge transfer excitons; photoluminescence; quantum efficiency
Categories
Funding
- National Science Foundation [1410249]
- Army Research Office [W911NF-15-1-0554ARO]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1410249] Funding Source: National Science Foundation
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We study the optoelectronic properties of a type-II heterojunction (HJ) comprising a monolayer of the transition metal dichalcogenide (TMDC), WS2, and a thin film of the organic semiconductor, 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA). Both theoretical and experimental investigations of the HJ indicate that Frenkel states in the organic layer and two-dimensional Wannier-Mott states in the TMDC dissociate to form hybrid charge transfer excitons at the interface that subsequently dissociate into free charges that are collected at opposing electrodes. A photodiode employing the HJ achieves a peak external quantum efficiency of 1.8 +/- 0.2% at a wavelength of 430 +/- 10 nm, corresponding to an internal quantum efficiency (IQE) as high as 11 +/- 1% in these ultrathin devices. The photoluminescence spectra of PTCDA and PTCDA/WS2 thin films show that excitons in the WS2 have a quenching rate that is approximately seven times higher than in PTCDA. This difference leads to strong wavelength dependence in IQE.
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