3-Mercaptopropionic, 4-Mercaptobenzoic, and Oleic Acid-Capped CdSe Quantum Dots: Interparticle Distance, Anchoring Groups, and Surface Passivation

Abstract

The optoelectronic properties of quantum dots are strongly controlled by the chemical nature of their surface-passivating ligands. In this work, we present the synthesis, characterization, and surface modification of CdSe quantum dots (QDs) and their application in solar cells. CdSe QDs were capped in oleic acid (OA), 3-mercaptopropionic acid (MPA), and 4-mercaptobenzoic acid (MBA). The QDs were characterized by transmission electron microscopy (TEM), UV-Vis absorption and emission spectrophotometry, thermogravimetric analyses, and 1H and 13C NMR. From TEM analysis, it has been observed that interparticle distance can be effectively controlled by the presence of different molecular size ligands. From the 1H and 13C NMR, specific types of interactions between the Cd2+ and the ligands have been observed. Although CdSe/OA presented larger interparticle distance as compared to CdSe/MPA and CdSe/MBA, the photocatalytic oxidation of the thiol groups on the surface of the MPA- and MBA-based quantum dots resulted in poor surface stabilization, ultimately resulting in poor power conversion efficiencies which were ca. 70% smaller than that of OA-based solar cell.

Ink-Lithography for Property Engineering and Patterning of Nanocrystal Thin Films

“…PbAc 2 -treated CdSe NC thin films show enhanced PL intensity, as acetate and Pb ions are known to effectively passivate CdSe NCs and increase PL intensity (Figure S9b–d). − …”

Use of 2D Nanoplatelets to Improve The Sensitivity in Hybrid Photodetector For Indirect X-Ray Imaging

“…The OA ligand is a kind of long-chain ligand that helps with dispersion in a solution, but has the disadvantage of interfering with charge transport between NPL particles [35]. In contrast, as short-chain ligands such as pyridine, 3-mecaptopropionic acid (MPA), and 1,2-ethylenedithiol (EDT) shorten the distance between CdSe NPL particles, they thereby increase interactions with organic material and improve charge transport properties [36,37]. Among these short-chain ligands, we chose to apply pyridine ligand in our experiments due to its good electrical conductivity.…”

Stable Photodetectors Based on Formamidinium Lead Iodide Quantum Well Perovskite Nanoparticles Fabricated with Excess Organic Cations

“…Additionally, the long ligands between 2D structures decrease the charge transfer in optoelectronic devices because of the perovskite nanosheets’ loose packing . Therefore, shorter spacer ligands are more effective in surface passivation while reducing the interlayer distance …”

“…33 Therefore, shorter spacer ligands are more effective in surface passivation while reducing the interlayer distance. 34 Recently, 2D perovskite nanoparticles have been used to fabricate high-performance photodetectors. For instance, Li et al 35 have demonstrated that the photoresponsivity of verticaltype photodetectors made of CH 3 NH 3 PbI 3 nanosheets as the active layer is as high as 36 mA W −1 at visible wavelength.…”

“…Although long spacer ligands (especially with bulky functional groups) are commonly used for the synthesis of QWs, they have higher steric hindrance and are not able to passivate the surface effectively. 34,61 FA + as a shorter spacer ligand can be expected to fill the unbound sites more effectively than the longer ligands [such as (BA) and (PEA)], probably resulting in better surface passivation. It is worth mentioning that, as it is depicted in Figure 2c, the PL intensity of the fresh CQW solution with an FAI/PbI 2 molar ratio of 2.6 remained approximately unchanged after 1 month, which demonstrates the higher stability of 2D structures under the humidified air (40%).…”