Abstract
Molybdenum disulphide (MoS2), which is a typical semiconductor from the family of layered transition metal dichalcogenides (TMDs), is an attractive material for optoelectronic and photodetection applications because of its tunable bandgap and high quantum luminescence efficiency. Although a high photoresponsivity of 880–2000 AW−1 and photogain up to 5000 have been demonstrated in MoS2-based photodetectors, the light absorption and gain mechanisms are two fundamental issues preventing these materials from further improvement. In addition, it is still debated whether monolayer or multilayer MoS2 could deliver better performance. Here, we demonstrate a photoresponsivity of approximately 104 AW−1 and a photogain of approximately 107 electrons per photon in an n-n heterostructure photodetector that consists of a multilayer MoS2 thin film covered with a thin layer of graphene quantum dots (GQDs). The enhanced light-matter interaction results from effective charge transfer and the re-absorption of photons, leading to enhanced light absorption and the creation of electron-hole pairs. It is feasible to scale up the device and obtain a fast response, thus making it one step closer to practical applications.
Highlights
Molybdenum disulphide (MoS2), which is a typical semiconductor from the family of layered transition metal dichalcogenides (TMDs), is an attractive material for optoelectronic and photodetection applications because of its tunable bandgap and high quantum luminescence efficiency
As a typical semiconductor from the family of TMDs, MoS2 has a tunable bandgap that varies with thickness; that is, bulk MoS2 has an indirect bandgap of 1.2 eV and, because of quantum confinement, monolayer MoS2 has a direct bandgap of 1.8 eV1–3
We suggest that a re-absorption of emitted photons from the graphene quantum dots (GQDs) by MoS2 is the origin of the PL quenching
Summary
Molybdenum disulphide (MoS2), which is a typical semiconductor from the family of layered transition metal dichalcogenides (TMDs), is an attractive material for optoelectronic and photodetection applications because of its tunable bandgap and high quantum luminescence efficiency. A high photoresponsivity of 880–2000 AW−1 and photogain up to 5000 have been demonstrated in MoS2-based photodetectors, the light absorption and gain mechanisms are two fundamental issues preventing these materials from further improvement. It is still debated whether monolayer or multilayer MoS2 could deliver better performance. By optimising the fabrication technique, photodetectors based on mechanically exfoliated monolayer MoS2 can achieve an impressively high responsivity of 880 AW−1 (Ref. 10). That multilayer MoS2 has a density of state that is three times higher than monolayer MoS218, as well as www.nature.com/scientificreports/
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