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Point-like photovoltaic junction in 2D semiconductor homobilayer
Nam Thanh Trung Vu1, Mingjun Chen2, Yi Wei Ho3,4
1Physics Department, National University of Singapore, Singapore, Singapore. vuttn@a-star.edu.sg.
Nature Nanotechnology
|August 14, 2026
Summary
Individual dopants in atomically thin semiconductors act as nanoscale photovoltaic units. These dopants, even at the atomic scale, drive charge separation and photocurrent generation in van der Waals homobilayers.
Area of Science:
- Solid-state physics
- Materials science
- Optoelectronics
Background:
- Atomically thin semiconductor junctions are crucial for exploring optoelectronic processes at reduced scales.
- The role of individual dopants in photovoltaic responses within atomic-scale junctions remains poorly understood.
Purpose of the Study:
- To investigate the microscopic photoresponse of van der Waals semiconductor homobilayers with ionizing acceptors.
- To elucidate the contribution of single dopants to photovoltaic effects in ultra-thin materials.
Main Methods:
- Utilized photoconductive atomic force microscopy (AFM) on vanadium-doped WSe2 (V:WSe2) bilayers.
- Analyzed vertical WSe2/V:WSe2 homobilayer devices.
- Performed photocurrent spectroscopy and quasi-classical modeling.
Main Results:
- Direct visualization of nanometre-scale photocurrent hotspots centered on individual dopants.
- Observed opposite current polarities for dopants in top and bottom layers of V:WSe2 bilayers.
- Demonstrated linear scaling of photocurrent with dopant concentration and a unique compensation voltage.
Conclusions:
- Charged dopants function as elementary photovoltaic units in atomically thin homobilayers.
- Dopants facilitate efficient exciton dissociation by converting intralayer excitons into charge-separated interlayer states within ~1 nm.
- Established dopant-defined point-like junctions as key to photovoltaic effects in these systems.
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