Dependence of Photocurrent Enhancements in Quantum Dot (QD)‐Sensitized MoS₂ Devices on MoS₂ Film Properties

Abstract

In this report we demonstrate highly efficient nonradiative energy transfer (NRET) from alloyed CdSeS/ZnS semiconductor nanocrystal quantum dots (QDs) to MoS2 films of varying layer thicknesses, including pristine monolayers, mixed monolayer/bilayer, polycrystalline bilayers and bulk-like thicknesses, with NRET efficiencies of over 90%. Large-area MoS2 films were grown on Si/SiO2 substrates by chemical vapor deposition (CVD). Despite the ultrahigh NRET efficiencies there is no distinct increase in the MoS2 photoluminescence intensity. However, by studying the optoelectronic properties of the MoS2 devices before and after adding the QD sensitizing layer photocurrent enhancements as large as ~14 fold for pristine monolayer devices are observed, with enhancements on the order of ~2 fold for MoS2 devices of mixed monolayer and bilayer thicknesses. For the polycrystalline bilayer and bulk-like MoS2 devices there is almost no increase in the photocurrent after adding the QDs. Industrially scalable techniques were specifically utilised to fabricate the samples studied in this report, demonstrating the viability of this hybrid structure for commercial photodetector or light harvesting applications.

Nonradiative Energy Transfer and Photocurrent Enhancements in Hybrid Quantum Dot-MoS<inf>2</inf> Devices

“…This behaviour is a consequence of the strong increase in dielectric screening with the addition of each MoS2 layer [4]. The incorporation of a sensitizing species on MoS2 photodetector devices has been shown to substantially increase the photocurrent and photoresponsivity of the devices [5]- [7]. In this contribution it is confirmed that the energy transfer mechanism in QD-sensitised MoS2 devices is Förster-type NRET.…”

“…One particular mechanism of energy transfer from the sensitizing species to the active material is Förster-type nonradiative energy transfer (NRET). This has been proven to be a highly efficient process in donor-acceptor pairs of quantum dots (QDs) and monolayer TMDs [3]- [5]. It has also been revealed that, in contrast to graphene, the NRET rate between QDs and MoS2 decreases as the layer number of the material increases.…”

Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector

“…An attractive method to overcome this thickness-limited absorption is to add a sensitizing material on top of the 2D material. There have been a few reports of dye sensitized [ 19 ] and quantum dot (QD) sensitized MoS 2 photodetectors [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. QDs in particular have the advantages of high quantum yield, broadband absorption, and tunable absorption wavelength by changing its size or composition.…”

Narrow‐Band QD‐Enhanced PIN Metal‐Oxide Heterostructure Phototransistor with the Assistance of Printing Processes

“…To date, the IGZO active layer has provided low modulated gate voltage, low subthreshold swing (SS), high on–off ratios and other electric properties for phototransistors . QDs and low‐dimensional materials can produce a high optoelectric conversion efficiency and rate, low dark current, high responsivity and detectivity for the phototransistor as a high‐performance integrated detector . However, key obstacles to their wide range of use in integrated‐photodetection applications must urgently be addressed.…”

“…[5,6] QDs and low-dimensional materials can produce a high optoelectric conversion efficiency and rate, low dark current, high responsivity and detectivity for the phototransistor as a high-performance integrated detector. [7][8][9][10][11] However, key obstacles to their wide range of use in integrated-photodetection applications must urgently be addressed. For example, the wide-band semiconductor nature of IGZO leads to a low www.advopticalmat.de under an IR wavelength (1.5 µm) that is comparable to that of a commercial III-IV photodetector.…”