The two degenerate valleys, K and K’, in 2D transition metal dichalcogenides (TMD) can be used as information carriers for quantum information science and technologies. Obtaining valley polarization in TMDs, which is the equivalent of encoding or writing data, is the first step towards these applications. Here, we report valley polarization in monolayer TMD/chiral perovskite heterostructures at room temperature via spin selective charge transfer. We obtained 7% degree of polarization from the heterostructures after photoexcitation with a linearly polarized laser. We further demonstrate that charge transfer occurs within picoseconds using ultrafast transient absorption spectroscopy. Our results pave the way for practical valleytronics devices based on TMD/perovskite heterostructures.
2D transition metal dichalcogenides have two degenerate valleys which can be used to store and process information for quantum computing and communications. Here we report robust valley polarization in monolayer TMDs/chiral perovskite heterostructures at room temperature. We control valley index in monolayer TMDs via spin selective charge extraction with chiral perovskite and obtain 7% degree of polarization. We further investigate the charge transfer dynamics in the heterostructures by measuring transient absorption using pump-probe spectroscopy and show that charge transfer from monolayer TMD to chiral perovskite occurs within sub-picosecond timescales. Our results pave the way for practical valleytronics devices based on TMD/perovskite heterostructures.
Mixed dimensional heterostructures incorporating monolayers of transition metal dichalcogenides (TMDs) and non-van Der Waals nanomaterials provide interesting physics at low dimensions and beyond that of pristine TMDs. Of particular interest are light stimulated interfacial phenomena where excitons and/or charge carriers induced in either components diffuse at the interface of the heterostructure to provide enhanced optical activity.
In this work we report ultrafast carrier dynamics in mixed 0D/2D PbS QD-monolayer MoS2 by transient absorption microscopy and time-resolved confocal luminesce. We show dependency of the rate for carrier transfer with PbS QD core size which we relate to changes in bandgap alignment at interface and resulting from changes in components band overlap and provide a mechanistic view of interfacial charge transfer via ultrafast transient absorption and emission microscopy.
We report a nanohybrid based on an atomically thin, two-dimensional (2D) van Der Waals semiconductor, colloidal quantum dots and a light harvesting protein where step-wise energy transfer takes place. We connect nanocomponents of the nanohybrid via electrostatic self-assembly and layer-by-layer polyelectrolyte deposition and utilize bandgap engineering to created conditions for efficient directional stepwise energy transfer, from quantum dots, to proteins and to the 2D van Der Waals semiconductor, molybdenum diselenide (MoSe2). The biotic/abiotic nanohybrid exhibits enhanced absorption cross section and enhanced light harvesting through the addition of quantum dots and proteins next to MoSe2, which in turn leads to enhanced exciton generation in MoSe2 via energy transfer from quantum dots to proteins and finally to MoSe2.
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