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Electronic Band Structure and Ultrafast Carrier Dynamics of Two Dimensional (2D) Semiconductor Nanoplatelets (NPLs) in the Presence of Electron Acceptor for Optoelectronic Applications

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journal contribution
posted on 16.11.2020, 09:29 by Avisek Dutta, Anusri Medda, Rajesh Bera, Ashima Rawat, Abir De Sarkar, Amitava Patra
Two-dimensional (2D) cadmium chalcogenide nanoplatelets (NPLs) have been grown as an emerging material for optoelectronic applications because of their unique properties. Here, we investigate the charge transfer dynamics of 2D CdSe NPLs in the presence of benzoquinone (BQ) molecule using steady-state and transient absorption (TA) spectroscopy. Atomic charge analysis affirms the transfer of electronic charges from the CdSe surface to the BQ molecule, resulting in bond formation, as suggested by the Cd–O bond length (2.52 Å) and the adsorption energy (−0.4 eV). Type II band alignment observed in the atom-projected band structure further attests to the electronic charge transfer from the conduction band of the CdSe surface to the LUMO of the BQ molecule. The BQ molecule raises the macroscopic static dielectric constant, which in turn lowers the exciton binding energy from 0.96 to 0.79 eV upon introducing the BQ molecule. It thereby facilitates the separation of electron–hole pairs in conformance to experimental results. The ultrafast electron transfer from CdSe NPLs to BQ and the reduction of electron–hole recombination processes are confirmed from ultrafast transient absorption spectroscopic study. Again 2D colloidal NPLs based hybrid device exhibits significant enhancement in photocurrent, higher responsivity, and detectivity (>104 times) than pure CdSe NPLs. Our findings reveal that 2D colloidal NPLs based hybrid offers a great opportunity for designing high-performance optoelectronic devices.

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