Combination of Cation Exchange and Quantized Ostwald Ripening for Controlling Size Distribution of Lead Chalcogenide Quantum Dots

Abstract

A new strategy for narrowing the size distribution of colloidal quantum dots (QDs) was developed by combining cation exchange and quantized Ostwald ripening. Medium-sized reactant CdS(e) QDs were subjected to cation exchange to form the target PbS(e) QDs, and then small reactant CdS(e) QDs were added which were converted to small PbS(e) dots via cation exchange. The small-sized ensemble of PbS(e) QDs dissolved completely rapidly and released a large amount of monomers, promoting the growth and size-focusing of the medium-sized ensemble of PbS(e) QDs. The addition of small reactant QDs can be repeated to continuously reduce the size distribution. The new method was applied to synthesize PbSe and PbS QDs with extremely narrow size distributions and as a bonus they have hybrid surface passivation. The size distribution of prepared PbSe and PbS QDs are as low as 3.6% and 4.3%, respectively, leading to hexagonal close packing in monolayer and highly ordered three-dimensional superlattice.

PbS Colloidal Quantum Dot Inks for Infrared Solar Cells

“…To improve the infrared photovoltaic performance of CQDSCs, various metal chalcogenide CQDs were studied, including PbS ( Cademartiri et al., 2006 ), PbSe ( Zhang et al., 2017a , 2017b , 2017c ), Ag 2 S ( Hwang et al., 2013 ), Ag 2 Se ( Tian et al., 2017 ), CuInS 2 ( Peer et al., 2017 ), and AgBiS 2 ( Huang et al., 2013 ) CQDs. Among these CQDs, PbS CQDs received more attention for the development of infrared solar cells in the wavelength region of 350–1,700 nm ( E g < 0.8 eV) and the PbS-based CQDSCs showed the highest efficiency of CQDSCs so far, which is very promising for the infrared solar cells.…”

Role of the Crystal Structure in Cation Exchange Reactions Involving Colloidal Cu2Se Nanocrystals

“… 10 − 12 The knowledge accumulated so far on CE reactions has enabled, this last year alone, the synthesis of new types of NHs, such as CdS nanowires covered by a monolayer of MoS 2 , 13 Cu 2 S-decorated CdS nanorods (NRs), 14 and new core@shell NC systems such as Mn 3 O 4 @CoMn 2 O 4 –Co x O y , 15 Ag–Zn–In-S@ZnS, 16 and SnTe@CdTe. 17 − 20 Moreover, the number of new NC materials that can be accessed by CE with control over the shape, 21 − 25 crystal structure, 26 and composition 27 − 34 has also increased significantly. In turn, these advanced nanostructures have found application in many different fields such as bioimaging, 16 , 20 , 28 , 30 , 35 chemical sensing, 30 supercapacitors, 21 electro- or photocatalysis, 14 , 15 and spintronic or optoelectronic devices.…”

PbE (E = S, Se) Colloidal Quantum Dot-Layered 2D Material Hybrid Photodetectors

“…However, there are still many avenues for continued progress in improving the figures of merit. There exists a wide and expanding array of studies of PbE QDs aimed at: controlling synthesis to improve size distribution and stability [155][156][157][158]; QD size and composition effects on the optoelectronic properties [39,49,159]; in-solution and layer-by-layer ligand exchange techniques [18,61]; and inter-and intra-layer charge transfer in QD films with other materials [28,45,160]. Many of these findings have yet to be applied to hybrid QD/2D material hybrid devices.…”