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Envisioning the Invisible: Controlled Exciton Binding and Dissociation in a Tunable Type-I to Type-II TMD Heterojunction


We exhibit interlayer exciton mediated electron trapping via in situ band engineering in a two-dimensional semiconductor. The band alignment of vertically stacked MoSe2/WS2 heterobilayers is tuned between type-I and type-II by application of an out-of-plane electric field through the heterojunction. Precision tuning of the energy alignment allows selective control over the formation of interlayer excitons (IX) which trap electrons at the atomic interface. We can drive field induced dissociation of IX freeing its constituent charge carriers. The band alignment and excitonic energies are mapped via photoluminescence and dark transport measurements, exciton injection into the heterobilayer is mapped via reflectance contrast, and charge carrier interactions are derived from photocurrent. These four different measurements are stitched together yielding a complete model of band alignment control and electron trapping. Using this model we are able to directly measure the binding energy of IX. These results provide a key contribution for next generation tunable quantum devices and exotic interaction based phenomena.

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