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- Santra, Pralay K., et al.
(författare)
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Molecular Ligands Control Superlattice Structure and Crystallite Orientation in Colloidal Quantum Dot Solids
- 2016
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 28:19, s. 7072-7081
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal quantum dot solids represent a new materials platform that has garnered interest for a variety of electronic, optoelectronic, and photovoltaic applications. In such solids, individual quantum dots must be coupled with each other to facilitate charge transport through the solid. Past improvements on charge transport of colloidal quantum dot solids have been achieved primarily through the control of the interparticle spacing. However, the role of morphological ordering of the crystalline facets of individual quantum dots on the charge transport of the quantum dot solid is unknown. Here, we show for the first time that small passivating ligand molecules around the quantum dots can control the arrangement of different facets of quantum dots within the quantum dot solid. The insights from this study provide important directions for future enhancement in orientation of quantum dots in colloidal quantum dot solids.
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- Beal, Rachel E., et al.
(författare)
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Structural Origins of Light-Induced Phase Segregation in Organic-Inorganic Halide Perovskite Photovoltaic Materials
- 2020
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Ingår i: Matter. - : Elsevier BV. - 2590-2393 .- 2590-2385. ; 2:1, s. 207-219
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Tidskriftsartikel (refereegranskat)abstract
- Organic-inorganic metal-halide perovskite materials offer a promising route to reducing the dollars-per-watt cost of solar energy due to their good optoelectronic properties and facile, scalable processing. Compositional tuning allows for the preparation of absorbers with band gaps tailor-made for specific tandem and single-junction applications, but photoinduced phase segregation in mixed-halide materials leads to the formation of low-band-gap regions that reduce the voltage of devices. This work explores the structural origins of photoinduced phase segregation in FA(y)Cs(1-y)Pb(BrxI1-x)(3) perovskite alloys. We use synchrotron X- ray diffraction to map the solvus between the cubic and cubic-tetragonal mixed-phase region and time-dependent photoluminescence to assess stability under illumination. We show that the correlation between crystallographic phase and phase-segregation behavior is imperfect, so phase is not the sole determinant of optical stability. Instead, we consider several possible mechanisms that could underlie the dependence of optical stability on perovskite composition.
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- Stone, Kevin H., et al.
(författare)
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Transformation from crystalline precursor to perovskite in PbCl2-derived MAPbI3
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the formation chemistry of metal halide perovskites is key to optimizing processing conditions and realizing enhanced optoelectronic properties. Here, we reveal the structure of the crystalline precursor in the formation of methylammonium lead iodide (MAPbI3) from the single-step deposition of lead chloride and three equivalents of methylammonium iodide (PbCl2 + 3MAI) (MA = CH3NH3). The as-spun film consists of crystalline MA2PbI3Cl, which is composed of one-dimensional chains of lead halide octahedra, coexisting with disordered MACl. We show that the transformation of precursor into perovskite is not favored in the presence of MACl, and thus the gradual evaporation of MACl acts as a self-regulating mechanism to slow the conversion. We propose the stable precursor phase enables dense film coverage and the slow transformation may lead to improved crystal quality. This enhanced chemical understanding is paramount for the rational control of film deposition and the fabrication of superior optoelectronic devices.
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