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Importance of ligands on TiO_2 nanocrystals for perovskite solar cells

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Chinese Physics B 2018年第1期27卷 92-97页

作者：赵耀赵怡程周文可伏睿李琪俞大鹏赵清 State Key laboratory for Mesoscopic Physics and electron microscopy laboratory School of Physics Peking University

The fabrication of high-quality electron-selective layers at low temperature is a prerequisite to realizing efficient flexible and tandem perovskite solar cells （PSCs）. A colloidal-quantum-dot ink that contains TiO2 nanocrystals enables the deposition of a flat film with matched energy level for PSCs; however, the selection of ligands on the TiO2 surface is still unexplored. Here, we systematically studied the effect of the titanium diisopropoxide bis（acetylacetonate）（TiAc2） ligand on the performance of PSCs with a planar n-i-p architecture. We prepared TiO2 nanocrystals from TiCI4 and ethyl alcohol with C1- ligands attached on its surface and we found that a tiny amount of TiAc2 treatment of as-prepared TiO2 nanocrystals in a mixed solution of chloroform and methyl alcohol can enhance PSC power conversion efficiency （PCE） from 14.7% to 18.3%. To investigate the effect of TiAc2 ligand on PSCs, TiO2 samples with different TiAc2 content were prepared by adding TiAc2 into the as-obtained TiO2 nanocrystal solution. We use x-ray photoelectron spectroscopy to identify the content of C1 so as to reveal that C1 ligands can be substituted by TiAc2. We speculate that the improvement in PCE originates from amorphous TiO2 formation on the TiO2 nanocrystal surface, whereby a single-molecule layer of amorphous TiO2 facilitates charge transfer between the perovskite film and the TiO2 electronic transport layer, but excessive TiAc2 lowers the PSC performance dramatically. We further prove our hypothesis by x-ray diffraction measurements. We believe the PCE of PSCs can be further improved by carefully choosing the type and changing the content of surface ligands on TiO2 nanocrystal.

关键词： TiAc2 TiO2 nanocrystal surface ligand perovskite solar cells

Distribution of serotonin 5-HT_(2A) and 5-HT_7 receptors in the Onuf’s nucleus of the rat spinal cord

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Neural Regeneration Research 2008年第8期3卷 853-857页

作者： Fanqing Zeng Chen Xu Ge Xu laboratory of electron microscopy Chongqing Medical University Chongqing 400016 China

BACKGROUND：Motoneurons from the Onuf’s nucleus of the spinal cord, which innervate the striated muscle of the pelvic floor, play an important role in erection, ejaculation, and urine control. Serotonin （5-hydroxytryptamine, 5-HT） regulates motoneuron activity from the Onuf’s nucleus of the spinal cord. However, few studies exist that describe 5-HT receptor distribution in the Onuf’s nucleus. In addition, the nature of the effects of 5-HT receptor on the innervating striated muscle of the pelvic floor is controversial. OBJECTIVE： To investigate the distribution of serotonin 5-HT2A and 5-HT7 receptors in motoneurons of Onuf’s nucleus in the spinal cord of male rats, and to analyze the relationship of 5-HT2A and 5-HT7 receptor to central modulation of urogenital function. DESIGN, TIME AND SETTING： The neural morphology experiment was performed at the Ultramicro-structure laboratory of Reproductive Medicine, Basic Medical College, Chongqing Medical University, China from April to December 2007. MATERIALS： Ten adult, Sprague Dawley rats （eight males and two females） were randomly divided into gender control group （n = 4, 50% male and 50% female） and a retrograde tracing group （n = 6, 100% male） Recombinant pseudorabies virus （PRV-152） was provided by Professor LW Enquist from Princeton University, USA. Rabbit anti-5-HT2A and 5-HT7 receptor antibodies were purchased from Diasorin, France. METHODS： In the gender control group, the spinal L5-6 segments were harvested, sliced, and then incubate antibodies specific against 5-HT2A or 5-HT7 receptors for immunohistochemical staining. In the retrograde tracing group, PRV-152 was separately injected into the right ischiocavernosus （ischiocavernosus subgroup, n = 3） and the right external urethral sphincter （external urethral sphincter subgroup, n = 3）. Four days after injection, L5-6 segments were harvested, sliced, and incubated with antibodies specific against 5-HT2A or 5-HT7 receptors for double-labeling immunofluorescence sta

关键词： 5-hydroxytryptamine receptor Onuf's nucleus retrograde tracing urogenital reflex

Atomic-scale roles of Zn element in age-hardened AlMgSiZn alloys

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Journal of Materials Science & Technology 2021年第11期70卷 105-112页

作者： N.N.Jiao Y.X.Lai S.L.Chen P.Gao J.H.Chen Center for High-Resolution electron microscopy College of Materials Science&EngineeringHunan UniversityChangsha410082China electron microscopy laboratory and International Center for Quantum Materials School of PhysicsPeking UniversityBeijing100871China

Adding alloying elements to improve the performances or the manufacturing processes of Al-Mg-Si alloys has long been a serious issue in developing advanced automotive aluminum *** Zn element,among those promising ones,has demonstrated positive alloying effects on Al-Mg-Si ***,the atomic-scale roles of Zn in an age-hardened Al-Mg-Si-Zn alloy have not been adequately *** atomic-resolution electron microscopy,here we report the precise locations of Zn elements in all hardening precipitates involved and their alloying mechanism at the atomic scale when alloying the *** results show that Zn atoms enter all the major hardening phases to occupy specific featured atomic sites of the original elements,*** Si1 and Mg2 sites in theβ’-2 phase,and modify their crystal structures,interfacial structures and morphologies in characteristic *** is revealed that for theβ’-phase,Zn atoms occupy unique atomic sites,whereas for other phases,they demonstrate similar behaviors as other additive alloying elements such as Ag and Cu do.

关键词： Al-Mg-Si alloy Zn addition Precipitate electron microscopy

Tapered dielectric structure in metal as a wavelength-selective surface plasmon polariton focuser

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Chinese Physics B 2009年第11期18卷 4865-4869页

作者：张洋赵清廖志敏俞大鹏 State Key laboratory for Mesoscopic Physics and Electron Microscopy LaboratorySchool of PhysicsPeking University

Symmetric tapered dielectric structures in metal have demonstrated applications such as the nanofocusing of surface plasmon polaritons, as well as the waveguiding of V-channel polaritons. Yet the fabrication of smooth-surfaced tapered structure remains an obstacle to most researchers. We have successfully developed a handy method to fabricate metal-sandwiched tapered nanostructures simply with electron beam lithography. Though these structures are slightly different from conventional symmetric V-shaped structures, systematic simulations show that similar functionality of surface plasmon polariton nanofocusing can still be achieved. When parameters are properly selected, wavelength- selective nanofocusing of surface plasmon polaritons can be obtained.

关键词： tapered structure surface plasmon focusing finite-difference time-domain

Effect of anneal pre-treatment of polycrystalline aluminum sheets on synthesis of highly-ordered anodic aluminum oxide membranes

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Science China(Technological Sciences) 2008年第11期51卷 1838-1842页

作者： ZHANG Lu ZHANG Xiao PAN CaoFeng ZHU Jing Beijing National Center for electron microscopy Lab of Advanced MaterialsDepartment of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Anodic aluminum oxide (AAO) membranes with large ordered pore domains were successfully prepared by adopting the anneal pre-treatment of polycrystalline alu- minum sheets. A statistical method with Gaussian distribution was introduced to quantitatively study the size of the domain with ordered pores. The largest average area of ordered pore domains was 2.6 μm2±0.11 μm2. The corresponding AAO membrane was synthesized by aluminum sheets annealed at 893 K for 24 h.

关键词： anodic aluminum oxide (AAO) annealing temperature annealing duration Gaussian distribution

In-situ evaluation for corrosion process at fusion boundary of stainless steel strip overlay joints in H2S containing solution

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中国有色金属学会会刊：英文版 2004年第Z1期14卷 413-419页

作者： ZOU Yang PAN Chun-xu FU Qiang Department of Physics & Center for electron microscopy Wuhan University Wuhan 430063 China Department of Physics & Center for Electron Microscopy Wuhan University Wuhan 430063 China Department of Physics & Center for Nano-Science and Technology Wuhan University Wuhan 430063 China

The present work studied the corrosion properties around the fusion boundaries of 2.25Cr-1Mo steel with stainless steel strip overlay joints under as welded condition and after post-weld heat treatment (PWHT) in H2 S containing solution (NACE TM-01-77 standard) with different time. An in-situ observation method was introduced for evaluating corrosive progress in the fusion boundary in H2 S containing solution, that is, the samples were marked firstly at the boundary and then treated in the solution for variant time. Each time after the corrosion treatment, the observations were kept to focus at the same marked area by using scanning electron microscopy (SEM) to observe the corrosion progress. The results reveal that the fusion boundary is the worst region for corrosion resistance when comparing with other boundaries, and a broad fusion boundary has a stronger resistance for "hydrogen induced disbonding" than a narrow one.

关键词： dissimilar steel welding fusion boundary H2S corrosion post-weld heat treatment

Anisotropic Inter-granular Corrosion Behaviors and Microstructures of AlMgSiCu Alloy Sheets Made by Thermal–Mechanical Treatments

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Acta Metallurgica Sinica(English Letters) 2022年第2期35卷 275-284页

作者： L.M.Liu Y.X.Lai C.L.Wu Z.Zhang J.H.Chen Center for High-Resolution electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

This study investigates the microstructure and local corrosion behavior of an Al-Mg-Si-Cu alloy,which has been subjected to cold-rolling with different deformation strain ratios(DSRs)and followed by artificial *** corrosion tests show that peak-aged samples with a small DSR(5-10%)are sensitive to inter-granular corrosion(IGC)along both the normal and rolling *** the DSR increases to medium strength(20-40%),IGC sensitivity decreases along both directions and corrosion propagates *** the DSR is 60-80%,IGC sensitivity along the normal direction continues to decrease,but increases along the rolling direction,indicating pronounced corrosion *** characterization reveals the decreased IGC sensitivity is mainly attributed to a reduction in element segregation at high-angle grain boundaries and the kinked and discontinuous grain boundary corrosion *** increased IGC sensitivity along the rolling direction could be related to the significantly flattened grains.

关键词： Al alloys Local corrosion Anisotropy Transmission electron microscopy(TEM) electron backscattering diffraction(EBSD)

Dislocation-Induced Precipitation and Its Strengthening of Al–Cu–Li–Mg Alloys with High Mg

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Acta Metallurgica Sinica(English Letters) 2021年第5期34卷 597-605页

作者： Xiangpeng Gong Shifang Luo Shiyong Li Cuilan Wu Center for High-Resolution electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha410082China

Generally, the good combination of pre-deformation and aging can improve the mechanical strength of the Al–Cu–Li–Mg alloys. However, the effects of pre-deformation on competitive precipitation relationship and precipitation strengthening have not been clarified in detail in Al–Cu–Li–Mg alloys with high Mg. In the present study, the effects of pre-deformation level on the microstructure and mechanical properties of an Al–2.95 Cu–1.55 Li–0.57 Mg–0.18 Zr alloy have been investigated. It is found that the introduction of dislocation by 5% pre-deformation can facilitate the precipitation of new successive composite precipitates and T _1 precipitates along the sub-grain boundaries or dislocations and inhibit the precipitation of dispersive GPB zones which is the main precipitates of the alloys without pre-deformation. The introduction of 5% pre-deformation can enhance the mechanical properties considerably. When the pre-deformation level increases from 5 to 15%, the number density of the successive composite precipitates and T _1 precipitates increases, and the aspect ratio of T _1 precipitates decreases. The decrease in T _1 precipitate aspect ratio and the increment of the successive composite precipitates result in the reduction in precipitation strengthening. Therefore, the increase in pre-deformation level from 5 to 15% does not further improve the mechanical properties of the alloys, although the dislocation strengthening increases continuously.

关键词： Aluminum alloys Precipitation behavior Pre-deformation Precipitation strengthening Dislocation strengthening

Revisiting the Hierarchical Microstructures of an Al-Zn-Mg Alloy Fabricated by Pre-deformation and Aging

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Acta Metallurgica Sinica(English Letters) 2020年第11期33卷 1518-1526页

作者： Xiong-Wei Yu Jiang-Hua Chen Wen-Quan Ming Xiu-Bo Yang Tian-Tian Zhao Ruo-Han Shen Yu-Tao He Cui-Lan Wu Center for High-Resolution electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

Pre-deformation before aging has been demonstrated to have a positive effect on the mechanical strength of the 7N01 alloy in our previous study,which is rather different from the general negative effects of pre-deformation on high-strength 7XXX aluminum *** order to explain the strengthening mechanism relating to the positive effect,in the present study,the microstructure of the aged 7N01 alloy with different degrees of pre-deformation was investigated in detail using advanced electron microscopy *** results show that,without pre-deformation,the aged alloy is strengthened mainly by the η′type of hardening *** contrast,with pre-deformation,the aged alloy is strengthened by the hierarchical microstructure consisting of the GP-η′type of precipitates formed inside sub-grains,the ηp type of precipitates formed at small-angle boundaries,and the dislocation introduced by pre-deformation(residual work-hardening effect).By visualizing the distribution of theηp precipitates through three-dimensional electron tomography,the 3 D microstructures of dislocation cells are clearly *** combinations of ηp precipitates,GP-η′precipitates and residual dislocations in the alloy are responsible for the positive effect of pre-deformation on its mechanical properties.

关键词： Aluminum alloys Precipitates Pre-deformation Three-dimensional electron tomography(3DET) Dislocation cell