| 1. |
- Cao, Qi, et al.
(författare)
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N-Type Conductive Small Molecule Assisted 23.5% Efficient Inverted Perovskite Solar Cells
- 2022
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Ingår i: Advanced Energy Materials. - : John Wiley & Sons. - 1614-6832 .- 1614-6840. ; 12:34
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Tidskriftsartikel (refereegranskat)abstract
- Because of the compatibility with tandem devices and the ability to be manufactured at low temperatures, inverted perovskite solar cells have generated far-ranging interest for potential commercial applications. However, their efficiency remains inadequate owing to various traps in the perovskite film and the restricted hole blocking ability of the electron transport layer. Thus, in this work, a wide-bandgap n-type semiconductor, 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-phenylpyrimidine (B4PyPPM), to modify a perovskite film via an anti-solvent method is introduced. The nitrogen sites of pyrimidine and pyridine rings in B4PyPPM exhibit strong interactions with the undercoordinated lead ions in the perovskite material. These interactions can reduce the trap state densities and inhibit nonradiative recombination of the perovskite bulk. Moreover, B4PyPPM can partially aggregate on the perovskite surface, leading to an improvement in the hole-blocking ability at its interface. This modification can also increase the built-in potential and upshift the Fermi level of the modified perovskite film, promoting electron extraction to the electron transport layer. The champion device achieves a high efficiency of 23.51%. Meantime, the sealed device retains approximate to 80% of its initial performance under a maximum power point tracking for nearly 2400 h, demonstrating an excellent operational stability.
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| 2. |
- Krieger, Jonas A., et al.
(författare)
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Weyl spin-momentum locking in a chiral topological semimetal
- 2024
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Ingår i: Nature Communications. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Spin-orbit coupling in noncentrosymmetric crystals leads to spin-momentum locking – a directional relationship between an electron’s spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin-momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin-momentum locking has remained elusive in experiments. Theory predicts that Weyl spin-momentum locking can only be realized in structurally chiral cubic crystals in the vicinity of Kramers-Weyl or multifold fermions. Here, we use spin- and angle-resolved photoemission spectroscopy to evidence Weyl spin-momentum locking of multifold fermions in the chiral topological semimetal PtGa. We find that the electron spin of the Fermi arc surface states is orthogonal to their Fermi surface contour for momenta close to the projection of the bulk multifold fermion at the Γ point, which is consistent with Weyl spin-momentum locking of the latter. The direct measurement of the bulk spin texture of the multifold fermion at the R point also displays Weyl spin-momentum locking. The discovery of Weyl spin-momentum locking may lead to energy-efficient memory devices and Josephson diodes based on chiral topological semimetals.
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| 3. |
- Wang, Shuangjie, et al.
(författare)
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Critical Role of Removing Impurities in Nickel Oxide on High-Efficiency and Long-Term Stability of Inverted Perovskite Solar Cells
- 2022
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Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 61:18
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Tidskriftsartikel (refereegranskat)abstract
- The performance enhancement of inverted perovskite solar cells applying nickel oxide (NiOx) as the hole transport layer (HTL) has been limited by impurity ions (such as nitrate ions). Herein, we have proposed a strategy to obtain high-quality NiOx nanoparticles via an ionic liquid-assisted synthesis method (NiOx-IL). Experimental and theoretical results illustrate that the cation of the ionic liquid can inhibit the adsorption of impurity ions on nickel hydroxide through a strong hydrogen bond and low adsorption energy, thereby obtaining NiOx-IL HTL with high conductivity and strong hole-extraction ability. Importantly, the removal of impurity ions can effectively suppress the redox reaction between the NiOx film and the perovskite film, thus slowing down the deterioration of device performance. Consequently, the modified inverted device shows a striking efficiency exceeding 22.62 %, and superior stability maintaining 92 % efficiency at a maximum power point tracking under one sun illumination for 1000 h.
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| 4. |
- Wang, Tong, et al.
(författare)
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Deep defect passivation and shallow vacancy repair via an ionic silicone polymer toward highly stable inverted perovskite solar cells
- 2022
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 15:10, s. 4414-4424
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Tidskriftsartikel (refereegranskat)abstract
- Additive engineering is an effective strategy for defect passivation and performance improvement of perovskite solar cells (PSCs). However, few additives have achieved outstanding stability with high efficiency by simultaneously passivating deep and shallow defects. Herein, we design a novel ionic silicone polymer (PECL) with multi-active sites as an additive to modify inverted PSCs. The C-O groups in the PECL polymer can chelate with undercoordinated Pb2+ and Pb clusters to passivate deep defects; and the ionic groups in the PECL polymer can generate electrostatic interaction with both positively and negatively charged vacancies, which help to repair shallow defects. Moreover, we quantitatively reveal the effect of deep and shallow defects on the efficiency and stability of PSCs separately, by establishing the correlation between additives with different functional groups and the performance of devices. Consequently, the power conversion efficiency of the PECL-modified inverted PSC increases from 20.02% to 23.11%. More importantly, the encapsulated PSCs maintain 95% of their initial steady-state power output after 1500 hours under AM 1.5 illumination at the maximum power point at 45 degrees C. Therefore, we provide a universal guideline of polymer structure design for defect healing in stabilizing PSCs with high efficiency.
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| 5. |
- Xing, Guozhong, et al.
(författare)
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Correlated d(0) ferromagnetism and photoluminescence in undoped ZnO nanowires
- 2010
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Ingår i: APPLIED PHYSICS LETTERS. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:11, s. 112511-
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Tidskriftsartikel (refereegranskat)abstract
- We report the correlated d(0) ferromagnetism and photoluminescence in undoped single-crystalline ZnO nanowires synthesized by using a vapor transport method. We systematically tune the oxygen deficiency in the ZnO nanowires from 4% to 20% by adjusting the growth conditions, i.e., selecting different catalyst (Au or Ag) and varying the growth temperature. Our study suggests that oxygen vacancies induce characteristic photoluminescence and significantly boost the room-temperature ferromagnetism. Such undoped ZnO nanowires with tunable magnetic and optical properties are promising to find applications in multifunctional spintronic and photonic nanodevices.
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| 6. |
- Yang, Jiabao, et al.
(författare)
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Inhibiting metal-inward diffusion-induced degradation through strong chemical coordination toward stable and efficient inverted perovskite solar cells
- 2022
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 15:5, s. 2154-2163
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Tidskriftsartikel (refereegranskat)abstract
- The inward diffusion of metal electrodes is one of the main reasons for the deterioration of the long-term device stability of perovskite solar cells (PSCs). Thus, herein, we adopt a simple additive engineering strategy to modify the barrier material bathocuproine (BCP) with 1,3,5-triazine-2,4,6-trithiol trisodium salt (TTTS). Different from the traditional physical blocking strategies, TTTS could prevent the metal electrodes (e.g., gold, silver, and copper) from diffusing inward through the strong chemical coordination between TTTS and the metal electrode. The TTTS additive also improved the conductivity and band structure of BCP, thus enhancing the ability of BCP to extract electrons from the perovskite layer to the electrode. Consequently, the inverted device modified with TTTS exhibited a high efficiency of 22.59%, which is among the highest efficiencies reported to date for inverted PSCs. More importantly, it showed excellent operational, ambient, and thermal stability. The target device maintained its initial efficiency with no loss under continuous one-sun illumination at maximum power point tracking after 1000 h (the champion device), 91% in air (50% +/- 5% RH) for 5000 h, and 93% after heating at 85 degrees C for 1500 h (average efficiency from ten devices).
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| 7. |
- Yang, Jiabao, et al.
(författare)
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Overcome Low Intrinsic Conductivity of NiOx Through Triazinyl Modification for Highly Efficient and Stable Inverted Perovskite Solar Cells
- 2022
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:9
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Tidskriftsartikel (refereegranskat)abstract
- Nickel oxide (NiOx) is a promising hole transport material in inverted organic-inorganic metal halide perovskite solar cells. However, its low intrinsic conductivity hinders its further improvement in device performance. Here, we employ a trimercapto-s-triazine trisodium salt (TTTS) as a chelating agent of Ni2+ in the NiOx layer to improve its conductivity. Due to the electron-deficient triazine ring, the TTTS complexes with Ni2+ in NiOx via a strong Ni2+-N coordination bond and increases the ratio of Ni3+:Ni2+. The increased Ni3+ concentration adjusts the band structure of NiOx, thus enhancing hole density and mobility, eventually improving the intrinsic conductivity of NiOx. As a result, the device with TTTS modification displays a champion power conversion efficiency (PCE) of 22.81%. The encapsulated device based on a modified-NiOx layer maintains 94% of its initial power output at the maximum power point and continuous one-sun illumination for 1000 h at 45 degrees C. In addition, the unencapsulated target devices also maintain 92% at 60 +/- 5% relative humidity and 25 degrees C in the air for 5000 h; and 91% at 85 degrees C in a nitrogen atmosphere for 1000 h. The research provides an effective strategy to enhance PCE and stability of inverted PSCs via modifying NiOx films with triazine molecule.
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| 8. |
- Yang, Lin, et al.
(författare)
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Colorimetric and Ratiometric Near-Infrared Fluorescent Cyanide Chemodosimeter Based on Phenazine Derivatives
- 2013
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 5:4, s. 1317-1326
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Tidskriftsartikel (refereegranskat)abstract
- Two new near-infrared chemodosimeters for cyanide anion based on 5,10-dihexyl-5,10-dihydrophenazine were designed and synthesized. With dicyano-vinyl groups as the recognition site and electron-withdrawing groups on both sides, probe 1 exhibited an intramolecular charge transfer (ICT) absorption band at 545 nm and emission band at 730 nm, respectively, and thus showed an ICT block process and realized an 'on-off" response after bilateral reaction with cyanide anions in CH3CN. Probe 2 utilized an unreactive formyl group instead of one of the two reactive dicyano-vinyl groups as the electron-withdrawing component. Due to the unilateral recognition process the ICT of probe 2 was redirected and lead to a remarkably colorimetric and ratiometric near-infrared (NIR) fluorescent response for cyanine. Both probes provided high sensitivity and selectivity with apparent response signals which can be observed by naked eyes, even in the copresence of various other interference anions. Optical spectroscopic techniques, NMR titration measurements, and density functional theory calculations were conducted to rationalize the sensing mechanisms of these two probes.
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| 9. |
- Li, Hongxia, et al.
(författare)
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Microscopic insights of phase-transition-induced vapor transport enhancement in porous media
- 2024
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Ingår i: International Journal of Multiphase Flow. - 0301-9322. ; 177
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Tidskriftsartikel (refereegranskat)abstract
- Vapor transport in porous media, often associated with liquid-vapor phase change, is an fundamental process in many emerging underground energy storage and extraction processes (i.e., seasonal solar thermal aquifer storage, geothermal extraction, extraterrestrial in-situ water extraction). By jointly using experimental imaging and numerical modeling at the micro-scale, we conduct mechanistic pore scale investigation of capillarity-dominated phase change dynamics and its influence on vapor transport in partially saturated porous rock micromodel. Strongly linked to surface roughness and wettability condition, the capillarity hinders water vaporization from rock surface micro/nano-structures as observed under the environmental scanning electron microscope. By varying the contact angle of 0°, 60°, and 120°, the lattice Boltzmann simulation shows the wettability-dependent vaporization process of capillary-hold water, where pores with hydrophilic surfaces contains significantly more liquid water than that of the hydrophobic ones under the same temperature. When saturated vapor flows through rock porous patterns, capillarity further induces water condensation on the strongly water-wet surfaces. Water condensation, yet forming water bridges/islands and causing the blockage of vapor diffusion, enhances the vapor diffusion ability counterintuitively. The reduction of diffusion path is revealed as the main reason by assessing the local vapor pressure distribution before and after the pore filling by condensate. The findings support the debatable enhancement mechanisms postulated by Philip and de Vries. This work offers the insightful interfacial hydrodynamics of vapor transport in porous media and potentially provides operational guidance for geothermal applications and beyond.
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| 10. |
- Zhang, Xiaoyu, et al.
(författare)
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Comparative Study on Pyrido[3,4-b]pyrazine-Based Sensitizers by Tuning Bulky Donors for Dye-Sensitized Solar Cells
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:4, s. 2760-2771
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells (DSSCs) with cobalt electrolytes have gained increasing attention. In this Research Article, two new pyrido[3,4-b]pyrazine-based sensitizers with different cores of bulky donors (indoline for DT-1 and triphenylamine for DT-2) were designed and synthesized for a comparative study of their photophysical and electrochemical properties and device performance and were also analyzed through density functional theory calculations. The results of density function theory calculations reveal the limited electronic communication between the biphenyl branch at the cis-position of N-phenylindoline and the indoline core, which could act as an insulating blocking group and inhibit the dye aggregation and charge recombination at the interface of TiO2/dye/electrolyte. As expected, DSSCs based on DT-1 with cobalt redox electrolyte gained a higher photoelectric conversion efficiency of 8.57% under standard AM 1.5 G simulated sunlight, with J(sc) = 16.08 mA cm(-2), V-oc = 802 mV, and FF = 0.66. Both electrochemical impedance spectroscopy (EIS) and intensity-modulated photovoltage spectroscopy (IMVS) suggest that charge recombination in DSSCs based on DT-1 is much less than that in their counterparts of DT-2, owing to the bigger donor size and the insulating blocking branch in the donor of DT-1.
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