Size and Solvation Effects on Electronic and Optical Properties of PbS Quantum Dots

Abstract

PbS quantum dots (QDs), among the most mature nanocrystals obtained by colloidal chemistry, are promising candidates in optoelectronic applications at various operational frequencies. QD device performances are often determined by charge transport, either carrier injection before photoemission or charge detection after photoabsorption, which is significantly influenced by the dielectric environment. Here, we present the electronic structure and the optical gap of PbS QDs versus size for various solvents calculated using ab initio methods including the many-body perturbation approaches. This study highlights the importance of the dielectric environment, pointing out 1) the non-negligible shift of the electronic structure due to the ground state polarization; 2) a substantial impact on the electronic bandgap. The electron-hole binding energy, which varies largely with the QD size and solvent, is well-described by 1 an electrostatic model. This study reveals the fundamental physics of size and solvation effects, which could be useful to design PbS QDs-based optoelectronic devices.

Optical gain and entanglement through dielectric confinement and electric field in InP quantum dots

“…Furthermore, it is evident that the dielectric constant of the host material causes a shift in the exciton energy towards higher values across all size ranges. The observed trend can be safely attributed to the self-polarization potential, as has been found both experimentally [52][53][54] and theoretically 55,56 in the case of InP quantum dots. The variation of the exciton binding energy across the various quantum dot (QD) diameters within the four distinct dielectric matrices is illustrated in Fig.…”

A first-principles study of optoelectronic properties and electric field modulation in PbS quantum dot/graphene hybrid systems

“…Therefore, the diameter of the PbS QDs established in this study is 2 nm, consistent with the size of PbS QDs commonly used in experimental studies 40,41 and larger than the size of PbS QDs typically used in computational studies. 42–44 Monolayer graphene was obtained by slicing from bulk graphite unit cells, followed by geometric relaxation, supercell expansion, and lattice vector transformation to obtain a periodic orthogonal slab model. The monolayer graphene contains a total of 416 carbon atoms, with lattice constants in the X and Y directions exceeding 3.2 nm to ensure that the PbS QDs are not affected by its periodic images.…”

Photoemission Insight on Narrow Band Gap PbS Quantum Dots Relevant for Infrared Imaging

“…Brown et al provided experimental evidence showing that the surface dipole associated with capping ligands induces a relative displacement of the valence band with respect to the Fermi level, allowing tunability of the carrier density. The energy shift is given by normalΔ E = N . μ ε 0 ε r where μ represents the dipole magnitude, N denotes the surface density of dipoles, ε 0 is the vacuum permittivity, and ε r is the dielectric constant. , This systematic approach was immediately utilized to design optimized pn junctions, leading to record power conversion efficiencies …”

“…r 0 (1) where μ represents the dipole magnitude, N denotes the surface density of dipoles, ε 0 is the vacuum permittivity, and ε r is the dielectric constant. 14,15 This systematic approach was immediately utilized to design optimized pn junctions, leading to record power conversion efficiencies. 16 In a groundbreaking study, Chuang et al proposed combining an iodine-capped PbS CQD layer with a thiolcapped layer, utilized as n-type and p-type layers, respectively, to form the pn junction.…”