Nonmonotonic Size Dependence in the Hole Mobility of Methoxide-Stabilized PbSe Quantum Dot Solids

Abstract

We present a facile procedure to fabricate p-type PbSe-based quantum dot solids with mobilities as large as 0.3 cm2 V–1 s–1. Upon partial ligand exchange of oleate-capped PbSe quantum dots with the methoxide ion, we observe a pronounced red shift in the excitonic transition in conjunction with a large increase in conductivity. We show that there is little correlation between these two phenomena and that the electronic coupling energy in PbSe quantum dot solids is much smaller than often assumed. However, we observe for the first time a nonmonotonic size dependence of the hole mobility, illustrating that coupling can nonetheless be dominant in determining the transport characteristics. We attribute these effects to a decrease in charging energy and interparticle spacing, leading to enhanced electronic coupling on one hand and enhanced dipole interactions on the other hand, which is held responsible for the majority of the red shift.

Direct Work Function Measurement by Gas Phase Photoelectron Spectroscopy and Its Application on PbS Nanoparticles

“…In a recent study of lead chalcogenide nanoparticles capped with the methoxide ion, no significant changes in the carrier concentration was found upon varying the nanoparticle diameter between 3.0 and 8.9 nm. 67 We therefore assume the carrier concentrations of the two PbS particle samples capped with MeO − used in this work to be of similar magnitude. In Figure 4, the Ar binding energies in the near surface region of the four PbS samples studied here are shown.…”

10.6% Certified Colloidal Quantum Dot Solar Cells via Solvent-Polarity-Engineered Halide Passivation

“…[17][18][19][20][21][22][23] The inherent large surface-to-volume ratio of QD materials results in unsaturated dangling bonds, creating undesired electronic trap states within the bandgap of QD solids. The ligand exchange procedure itself is prone to create new, rather than passivate existing, dangling bonds.…”

Quantifying Angular Correlations between the Atomic Lattice and the Superlattice of Nanocrystals Assembled with Directional Linking

“…34 Since the optoelectronic properties of PbS NC ensembles bear many opportunities for applications in solar cells or photodetectors, a number of ligand exchange procedures with small organic or inorganic molecules as well as single atom passivation strategies have been developed, all of which greatly increase the carrier mobilities within the SL of NCs. 28,33,[35][36][37][38][39][40][41][42][43][44] Due to the short interparticle spacing imposed by these ligands, structural coherence is mostly lost in such superlattices, but in rare cases it has been demonstrated that significant long-range order and even mesocrystallinity can be preserved. 25,35,45 However, a persisting problem of these protocols is that they are prone to introduce defects in the superlattice structure with some degree of granularity and significantly smaller grain sizes, which poses difficulties in determining the angular correlation with a meaningful statistical distribution.…”