ADVANCED MATERIALS
·
2019
·Vol. 31
·期 25
·1901284
·
IF 25.809
Minchao Qin,Kinfai Tse,Tsz-Ki Lau,Yuhao Li,Chun-Jen Su,Guang Yang,Jiehuan Chen,Junyi Zhu,U-Ser Jeng,Gang Li,Hongzheng Chen,Xinhui Lu
Mixed perovskites have achieved substantial successes in boosting solar cell efficiency, but the complicated perovskite crystal formation pathway remains mysterious. Here, the detailed crystallization process of mixed perovskites (FA 0.83 MA 0.17 Pb(I 0.83 Br 0.17 ) 3 ) during spin-coating is revealed by in situ grazing-incidence wide-angle X-ray scattering measurements, and three phase-formation stages are identified: I) precursor solution; II) hexagonal δ-phase (2H); and III) complex phases including hexagonal polytypes (4H, 6H), MAI–PbI 2 –DMSO intermediate phases, and perovskite α-phase. The correlated device performance and ex situ characterizations suggest the existence of an “annealing window” covering the duration of stage II. The spin-coated film should be annealed within the annealing window to avoid the formation of hexagonal polytypes during the perovskite crystallization process, thus achieving a good device performance. Remarkably, the crystallization pathway can be manipulated by incorporating Cs + ions in mixed perovskites. Combined with density functional theory calculations, the perovskite system with sufficient Cs + will bypass the formation of secondary phases in stage III by promoting the formation of α-phase both kinetically and thermodynamically, thereby significantly extending the annealing window. This study provides underlying reasons of the time sensitivity of fabricating mixed-perovskite devices and insightful guidelines for manipulating the perovskite crystallization pathways toward higher performance.
研究领域:
材料科学
·
光伏技术
·
晶体学
·
薄膜制备
·
X射线散射
✓ 已验证
DOI
高影响因子
Surfaces and Interfaces
·
2025
·
IF 6.3
Shan Zhu,Xudong Gong,Chengyun Fu,Qiang Tian,Zhichao Zhu,Chang Huang,Minhao Yan,Mark J. Henderson
The purpose of the study was to investigate the thermal stability of uranyl mineral phases that should occur as a result of corrosion of spent nuclear fuel in a deep geological waste repository. Crystallographic textures of two crystalline uranium oxyhydroxide films, metaschoepite and a lanthanum(III)-intercalated phase, precipitated on silicon, by grazing-incidence wide angle X-ray scattering (GIWAXS) in vacuo up to 200 °C were investigated. The X-ray data are supported by SEM-EDS measurements before and after thermal evacuation, as well as thermogravimetric analysis of powders in air up to 800 °C. The lanthanum-intercalated phase exhibited higher water desorption temperature, and a greater thermal stability compared with metaschoepite. These results are consistent with interactions between La(III) and water interactions, the formation of La(III)-hydrate layers that kept apart the uranyl polyhedral sheets. Grazing-incidence X-ray diffraction (GIXRD) revealed a progressive inability of aqua cations of early (Pr), mid-series (Sm, Gd, Tb, Dy) and late series (Ho, Er, Tm, Yb, Lu plus Y) rare earths to interact with metashoepite at 70 °C.
研究领域:
材料科学
·
核化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Small
·
2023
·Vol. 19
·期 47
·2303885
·
IF 13.3
Yuhao Li,Minchao Qin,Yunfan Wang,Shiang Li,Zhaotong Qin,Sai-Wing Tsang,Chun-Jen Su,Yubin Ke,Xinhui Lu
The black-to-yellow phase transition in perovskite quantum dots (QDs) is more complex than in bulk perovskites, regarding the role of surface energy. Here, with the assistance of in situ grazing-incidence wide-angle and small-angle X-ray scattering (GIWAXS/GISAXS), distinct phase behaviors of cesium lead iodide (CsPbI 3 ) QD films under two different temperature profiles–instant heating-up (IHU) and slow heating-up (SHU) is investigated. The IHU process can cause the phase transition from black phase to yellow phase, while under the SHU process, the majority remains in black phase. Detailed studies and structural refinement analysis reveal that the phase transition is triggered by the removal of surface ligands, which switches the energy landscape. The lattice symmetry determines the transition rate and the coexistence black-to-yellow phase ratio. The SHU process allows longer relaxation time for a more ordered QD packing, which helps sustain the lattice symmetry and stabilizes the black phase. Therefore, one can use the lattice symmetry as a general index to monitor the CsPbI 3 QD phase transition and finetune the coexistence black-to-yellow phase ratio for niche applications.
研究领域:
材料科学
·
纳米技术
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of the American Chemical Society
·
2026
·
IF 16.6
Yu Liu,Xu Zhang,Xingfan Zhang,Mingdong Zhou,Xiaolong Li,Fumin Wang,Xubin Zhang,Alexey A. Sokol,You Lu,Thomas W. Keal,Weiwei Tang,C. Richard A. Catlow,Junbo Gong
Gas–liquid interfacial nucleation can influence organic crystallization, yet its mechanistic role in polymorph selection remains poorly understood. Here, we demonstrate that nucleation at the gas–liquid interface of flufenamic acid solutions governs polymorph selection and gives rise to a pronounced concentration-dependent polymorphism, wherein low initial concentrations favor the nucleation of form I, higher concentrations yield form III, and intermediate concentrations selectively produce the metastable form IV. In situ synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS) directly resolves the formation and evolution of prenucleation assemblies at the interface, revealing three distinct interfacial molecular evolution pathways correlated with the emergence of specific polymorphs. Molecular dynamics (MD) simulations combined with energy calculations within the hybrid quantum mechanics/molecular mechanics (QM/MM) embedded-cluster framework further reveal interfacial enrichment, orientational bias, and conformer-dependent stabilization of stacking motifs, providing a microscopic interpretation of the experimentally observed selectivity. Together, these results establish the gas–liquid interface as an active structural selector that reshapes molecular organization prior to nucleation, offering a mechanistic framework for understanding and controlling polymorphism in evaporation-driven crystallization.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
MACROMOLECULES
·
2019
·
IF 5.997
Yuhan Wei,Jiliang Tian,Zekun Zhang,Chenhui Zhu,Jing Sun,Zhibo Li
Supramolecular two-dimensional (2D) nanomaterials from block copolymers have received great interest for their unique structure and properties. Here, we report the formation of ultrathin nanosheets from self-assembly of amphiphilic poly(ethylene glycol)-b-poly(N-(2-phenylethyl)glycine) (PEG-b-PNPE) diblock copolymers, which contain rigid crystallizable polypeptoid segment. The PEG-b-PNPE copolymers were synthesized via ring opening polymerization (ROP). The obtained PEG-b-PNPE diblock copolymers can spontaneously form highly ordered structures in PEG selective solvents such as water and methanol. The copolymers with short PNPE segment can directly form nanosheets in water, and the obtained 2D nanosheets have a uniform thickness of 4–5 nm. In contrast, the copolymers with relatively long PNPE segment can only assemble into nanosheets with the assistance of methanol. It is proposed that the crystallization and π–π stacking of PNPE blocks play critical roles in the formation of the nanosheet as suggested by grazing incidence wide-angle X-ray scattering (GIWAXS). During the process of adding water into copolymer methanol solution, the nanosheets were observed to evolve from individual nanofibers, to parallel aligning nanofibers, and eventually to the nanosheet structures verified by transmission electron microscopy (TEM) and cryo-TEM characterizations. We demonstrated that the preassembled filament behave as a fundamental packing motif to align laterally and further fuse into platelet-like structures. The assembly structure evolution process was tracked by TEM, atomic force microscopy, and cryo-TEM techniques. The understandings of supramolecular 2D nanosheet formation offer a new opportunity to make hierarchical nanostructures from polypeptoids containing copolymers.
研究领域:
材料科学
·
纳米技术
·
高分子化学
·
超分子化学
✓ 已验证
产品关联
DOI
高影响因子
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