Structure and Charge Carrier Dynamics in Colloidal PbS Quantum Dot Solids

Chen, Wei; Zhong, Jinhong; Li, Junzi; Saxena, Nitin; Kreuzer, Lucas P.; Liu, Haochen; Song, Lin; Su, Bo; Yang, Dan; Wang, Kun; Schlipf, Johannes; Körstgens, Volker; He, Tingchao; Wang, Kai; Müller‐Buschbaum, Peter

doi:10.1021/acs.jpclett.9b00869

Cited by 37 publications

(43 citation statements)

References 54 publications

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“…[ 35 ] For the octahedral shape, the QDs are prone to a stack with a body‐centered cubic/tetragonal (BCC/BCT) layout according to the Wigner–Seitz close packed construction, which is driven by the decrease of the total surface energy of the particle system. [ 35–36 ] The GISAXS results are in good agreement with the expected stacking behavior for the different QD shapes (see Figure ). QDs synthesized under thermodynamics‐dominated growth conditions are denoted as truncated‐octahedral ( to )‐QDs according to their expected shape and those synthesized under kinetics‐dominated growth conditions are denoted as nearly octahedral ( o )‐QDs.…”

Section: Resultssupporting

confidence: 77%

Facet Control for Trap‐State Suppression in Colloidal Quantum Dot Solids

Xia

Chen

Zhang

et al. 2020

Adv Funct Materials

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Trap states in colloidal quantum dot (QD) solids significantly affect the performance of QD solar cells, because they limit the open-circuit voltage and short circuit current. The {100} facets of PbS QDs are important origins of trap states due to their weak or missing passivation. However, previous investigations focused on synthesis, ligand exchange, or passivation approaches and ignored the control of {100} facets for a given dot size. Herein, trap states are suppressed from the source via facet control of PbS QDs. The {100} facets of ≈3 nm PbS QDs are minimized by tuning the balance between the growth kinetics and thermodynamics in the synthesis. The PbS QDs synthesized at a relatively low temperature with a high oversaturation follow a kinetics-dominated growth, producing nearly octahedral nanoparticles terminated mostly by {111} facets. In contrast, the PbS QDs synthesized at a relatively high temperature follow a thermodynamics-dominated growth. Thus, a spherical shape is preferred, producing truncated octahedral nanoparticles with more {100} facets. Compared to PbS QDs from thermodynamics-dominated growth, the PbS QDs with less {100} facets show fewer trap states in the QD solids, leading to a better photovoltaic device performance with a power conversion efficiency of 11.5%.

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Section: Resultssupporting

confidence: 77%

Facet Control for Trap‐State Suppression in Colloidal Quantum Dot Solids

Xia

Chen

Zhang

et al. 2020

Adv Funct Materials

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“…Tracking these peak shifts provides a feasible way to describe the inner energetic disorder for the exciton recombination. The exciton diffusion rate is fitted by Equation () [ 55 ]

\begin{matrix} true \\ right E ((), t) = E_{0} + normalΔ E \exp ((), - k_{normalΔ E} t) \end{matrix}

in which E ( t ) is the real‐time energy peak position, and E 0 is the final equilibrium energy state (equilibrium state i in Figure 8 a,c) for exciton recombination. Δ E is the energy gap between the initial excited state and equilibrium state i , which can be used to describe the energetic disorder of the film.…”

Section: Resultsmentioning

confidence: 99%

In Situ Growth of All‐Inorganic Perovskite Single Crystal Arrays on Electron Transport Layer

Tang

Chen

et al. 2020

Advanced Science

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Directly growing perovskite single crystals on charge carrier transport layers will unravel a promising route for the development of emerging optoelectronic devices. Herein, in situ growth of high‐quality all‐inorganic perovskite (CsPbBr3) single crystal arrays (PeSCAs) on cubic zinc oxide (c‐ZnO) is reported, which is used as an inorganic electron transport layer in optoelectronic devices, via a facile spin‐coating method. The PeSCAs consist of rectangular thin microplatelets of 6–10 µm in length and 2–3 µm in width. The deposited c‐ZnO enables the formation of phase‐pure and highly crystallized cubic perovskites via an epitaxial lattice coherence of (100)CsPbBr3∥(100)c‐ZnO, which is further confirmed by grazing incidence wide‐angle X‐ray scattering. The PeSCAs demonstrate a significant structural stability of 26 days with a 9 days excellent photoluminescence stability in ambient environment, which is much superior to the perovskite nanocrystals (PeNCs). The high crystallinity of the PeSCAs allows for a lower density of trap states, longer carrier lifetimes, and narrower energetic disorder for excitons, which leads to a faster diffusion rate than PeNCs. These results unravel the possibility of creating the interface toward c‐ZnO heterogeneous layer, which is a major step for the realization of a better integration of perovskites and charge carrier transport layers.

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“…face-centered cubic (fcc), body-centered cubic (bcc), and body-centered tetragonal (bct), detected either ex situ or in situ have been reported. 11,12,15,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] The origin of various observed superlattice structures and the different degree of ordering are believed to be caused by differences in NC size, shape, dispersity, composition, ligand length and ligand grafting density, NC concentration, assembly pathway (e.g., solvent evaporation or destabilization by antisolvent diffusion), cell/assembly geometry, rate of the assembly process, ligand-solvent and ligand-ligand interactions, or a combination thereof. 11,12,15,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] In this study, we use a recently designed custom-made sample environment for in situ SAXS measurements in transmission mode described in detail in Ref.…”

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confidence: 99%

Coexistence of hcp and bct Phases during In Situ Superlattice Assembly from Faceted Colloidal Nanocrystals

Lokteva

Koof

Walther

et al. 2019

J. Phys. Chem. Lett.

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We study the in situ self-assembly of faceted PbS nanocrystals from colloidal suspensions upon controlled solvent evaporation using time-resolved small-angle X-ray scattering and X-ray crosscorrelation analysis. In our bulk-sensitive experiment in transmission geometry, the superlattice crystallization is observed in real time revealing a hexagonal closed-packed (hcp) structure followed by formation of a body-centered cubic (bcc) superlattice. The bcc superlattice undergoes continuous tetragonal distortion in the solvated state shortly after its formation, resulting in the body-centered tetragonal (bct) structure. Upon solvent evaporation, the bct superstructure becomes more pronounced with the still coexisting hcp phase. These findings corroborate the existing simulations of assembling cuboctahedral-shaped particles and illustrate that we observed the predicted equilibrium states. This work is essential for a deeper understanding of the fundamental forces that direct nanocrystal assembly including nanocrystal shape and ligand coverage. TOC GRAPHICSKEYWORDS. Small angle X-ray scattering (SAXS), X-ray cross correlation analysis (XCCA), evaporative induced self-assembly, lead sulfide (PbS), time-resolved superlattice crystallization.

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Structure and Charge Carrier Dynamics in Colloidal PbS Quantum Dot Solids

Cited by 37 publications

References 54 publications

Facet Control for Trap‐State Suppression in Colloidal Quantum Dot Solids

Facet Control for Trap‐State Suppression in Colloidal Quantum Dot Solids

In Situ Growth of All‐Inorganic Perovskite Single Crystal Arrays on Electron Transport Layer

Coexistence of hcp and bct Phases during In Situ Superlattice Assembly from Faceted Colloidal Nanocrystals

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