Atomistic tight-binding theory of structural and optical properties in PbX (X = S, Se, and Te) nanocrystals
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Atomistic tight-binding theory of structural and optical properties in PbX (X 5 S, Se, and Te) nanocrystals Worasak Sukkabot1,a) 1
Department of Physics, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand Address all correspondence to this author. e-mail: [email protected]
a)
Received: 10 December 2019; accepted: 6 February 2020
The computational tool integrating empirical tight binding and full configuration interaction method is utilized to study the structural and optical properties of spherical PbX (X 5 S, Se, and Te) nanocrystals under various diameters. The nanocrystal architecture plays an essential role in the control of the structural and optical properties. The appearance of the quantum confinement is caused by the reduction of the optical band gaps with the increasing diameters. By changing the chalcogenide types and diameters, the band gaps are modified, with their wavelengths from 380 to 2500 nm, technologically applying for the visible and near-infrared optical devices. The tight-binding band gaps agree well with previously published theoretical and experimental values. The atomistic electron–hole interactions are mainly influenced by the diameters and chalcogenide types. Using the Stokes shift and fine structure splitting, PbS nanocrystal with the immense size may be implemented as a source of entangled photon pairs and optical filter. Finally, the theoretical study reveals the distinctive properties of PbX (X 5 S, Se, and Te) nanocrystals by changing their architecture for applications in optoelectronic devices and microscopy.
Introduction Semiconductor nanocrystals have been studied extensively as candidate materials for electronic, optical, and biological applications because of their distinct physical properties. In the comparison with II–VI nanocrystals, lead chalcogenide nanocrystals (PbS, PbSe, and PbTe) are better appropriate for the study because of their large Bohr exciton and dielectric constants. The large Bohr exciton introduces a strong confinement of the electron–hole pair. Lead chalcogenide nanocrystals are of prime importance for scientific and technological interests because of their tunable optical properties, hence leading to the applications operating in the near-infrared spectral regime [1, 2, 3, 4, 5, 6] and technological applications in photovoltaics [7, 8, 9, 10]. Owing to the advantages mentioned earlier, it is very authoritative to exploit the systematic studies to deliver and analyze the comprehensive information. For instance, Kane et al. [11] used the semiempirical tight-binding method to study the electronic structure of spherical PbS nanocrystals. The band gaps agreed with previously published experimental values. Hines and Scholes [12] synthesized PbS quantum dots using organometallic
ª Materials Research Society 2020
precursors. PbS nanocrystals showed the tunable and strong near-infrared optical property. By the demonstration from Litvin et al. [13], PbS nanocrystals of diameter in the 3.2– 6.9 nm range revealed temperature dependenc
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