| 1. |
- Choi, Hyeon-Seo, et al.
(författare)
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Oriented Crystal Growth during Perovskite Surface Reconstruction
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:45, s. 51149-51156
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Tidskriftsartikel (refereegranskat)abstract
- Surface passivation has become a key strategy for an improvement in power conversion efficiency (PCE) of perovskite solar cells (PSCs) since PSCs experienced a steep increase in PCE and reached a comparably matured point. Recently, surface passivation using a mixed salt of fluorinated alkyl ammonium iodide and formamidinium bromide demon-strated a remarkable improvement in both performance and stability, which can be tuned by the length of the alkyl chain. Nevertheless, the role of the alkyl chain in manipulating surface-limited crystal growth was not fully understood, preventing a further progress in interface control. In this study, we found that the length of the fluorine-substituted alkyl chain governed the crystal formation dynamics by manipulating surface tensions of different crystal orientations. The overall enhancement of the (001) plane, being the most favored, commonly resulted from the surface reformation of the perovskite film regardless of the chain length, while the highly oriented (001) over (111) was monitored with a particular chain length. The enhanced crystal orientation during surface recrystallization was responsible for the low trap density and thus effectively suppressed charge recombination at the interface, resulting in a considerable increase in open-circuit voltage and fill factor.
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| 2. |
- Nan, Beiya, et al.
(författare)
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Microstructure and Properties of Porous SiC Ceramics Modified by CVI-SiC Nanowires
- 2019
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Ingår i: Advanced Engineering Materials. - : Wiley. - 1438-1656 .- 1527-2648. ; 21:5
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Tidskriftsartikel (refereegranskat)abstract
- Sintered porous SiC ceramics are modified with SiC nanowires prepared via chemical vapor infiltration (CVI). SiC nanowires are successfully grown within sintered porous SiC ceramics following vapor-liquid-solid growth. The diameter of the SiC nanowires is in the range of 200 nm-1 mu m, and first decreases with increasing input gas ratio (alpha = 50, 60, 70, and 80) and increases thereafter. The diameter of the nanowires decreases from the surface to the interior areas of the porous SiC ceramics. SiC nanowires effectively improve the mechanical properties of the porous SiC ceramics, and sample Ni-50 has the highest flexural strength of 33.91 MPa and fracture toughness of 0.79 MPa center dot m(1/2), which increases by 90.4% and 49.1% compared to an unmodified sample, respectively. Additionally, the presence of SiC nanowires leads to porous SiC ceramics with altered porosity and microstructure, and higher thermal conductivity. The porous SiC ceramics modified by CVI SiC nanowires satisfy the requirements of gas filtration applications and the pressure drop increases with decreasing apparent porosity. The porous SiC ceramics modified with CVI SiC nanowire has higher permeability than those resulting from the introduction of CVI-SiC matrix or CVD-SiC coating into porous SiC ceramics.
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| 3. |
- You, Qiangwei, et al.
(författare)
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Microstructure and properties of porous SiC ceramics by LPCVI technique regulation
- 2017
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 43:15, s. 11855-11863
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Tidskriftsartikel (refereegranskat)abstract
- A new gradient pore structure in porous SiC ceramics was fabricated by low pressure chemical vapor infiltration (LPCVI). Effects of deposition duration on the mechanical properties and permeability of porous SiC ceramics were investigated. Results demonstrated that pore diameter and shapes decreased from the surface to the interior along with LPCVI duration. Porous SiC ceramics with deposition duration of 160 h exhibited flexural strength of 48.05 MPa and fracture toughness of 1.30 MPa m(1/2), where 221% and 189% improvements were obtained compared to porous SiC ceramics without LPCVI, due to CVI-SiC layer strengthening effect. Additionally, at the same gas velocity, pressure drop increase rate was faster due to apparent porosity and pore size change.
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