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Mingxing Li1 Percy Zahl1 Chang-Yong Nam1 Mircea Cotlet1

1, Brookhaven National Laboratory, Upton, New York, United States

Atomically thin transition metal dichalcogenides (TMDCs) have intriguing nanoscale properties like high charge mobility and photosensitivity, layer-thickness-dependent bandgap, mechanical flexibility, all appealing for the development of next generation optoelectronic, catalytic and sensory devices. Their atomically thin thickness however renders TMDCs poor absorptivity. Here we combine bilayer MoS2 with core-only CdSe QDs and core/shell CdSe/ZnS QDs to obtain hybrids with increased light harvesting and exhibiting interfacial charge transfer (CT) and nonradiative energy transfer (NET), respectively. Field-effect transistors (FETs) based on these hybrids and their responses to varying laser power and applied gate voltage were investigated with scanning photocurrent microscopy (SPCM) in view of their potential utilization in light harvesting and photodetector applications. We found CdSe-MoS2 hybrids to exhibit encouraging properties for photodetectors under low light exposure while CdSe/ZnS-MoS2 hybrids showed an enhanced charge carrier generation with increased light exposure, making them suitable for photovoltaics. While distinguishing optically between CT and NET in QD-TMDCs is non-trivial, we found they can be differentiated by SPCM as these two processes exhibit distinctive light-intensity dependencies: CT causes a photo-gating effect, decreasing the photocurrent response with increasing light power while NET increases the photocurrent response with increasing light power, opposite to the CT case.

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