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- ItemTowards low-temperature processing of efficient γ-CsPbI3 perovskite solar cells(London [u.a.] : RSC, 2023) Zhang, Zongbao; Ji, Ran; Hofstetter, Yvonne J.; Deconinck, Marielle; Brunner, Julius; Li, Yanxiu; An, Qingzhi; Vaynzof, YanaInorganic cesium lead iodide (CsPbI3) perovskite solar cells (PSCs) have attracted enormous attention due to their excellent thermal stability and optical bandgap (∼1.73 eV), well-suited for tandem device applications. However, achieving high-performance photovoltaic devices processed at low temperatures is still challenging. Here we reported a new method for the fabrication of high-efficiency and stable γ-CsPbI3 PSCs at lower temperatures than was previously possible by introducing the long-chain organic cation salt ethane-1,2-diammonium iodide (EDAI2) and regulating the content of lead acetate (Pb(OAc)2) in the perovskite precursor solution. We find that EDAI2 acts as an intermediate that can promote the formation of γ-CsPbI3, while excess Pb(OAc)2 can further stabilize the γ-phase of CsPbI3 perovskite. Consequently, improved crystallinity and morphology and reduced carrier recombination are observed in the CsPbI3 films fabricated by the new method. By optimizing the hole transport layer of CsPbI3 inverted architecture solar cells, we demonstrate efficiencies of up to 16.6%, surpassing previous reports examining γ-CsPbI3 in inverted PSCs. Notably, the encapsulated solar cells maintain 97% of their initial efficiency at room temperature and under dim light for 25 days, demonstrating the synergistic effect of EDAI2 and Pb(OAc)2 in stabilizing γ-CsPbI3 PSCs.
- ItemEvaluation of Sonocatalytic and Photocatalytic Processes Efficiency for Degradation of Humic Compounds Using Synthesized Transition-Metal-Doped ZnO Nanoparticles in Aqueous Solution(New York, NY [u.a.] : Hindawi, 2021) Maleki, Afshin; Seifi, Mehran; Marzban, NaderThe existence of a humic substance in water causes the growth of microorganisms and reduces the quality of water; therefore, the removal of these materials is crucial. Here, the ZnO nanoparticles doped using transition metals, copper (Cu) and manganese (Mn), were used as an effective catalyst for photocatalytic removal of humic substances in an aqueous environment under ultraviolet, visible light, and light-emitting diode irradiations. Also, we study the effect of the sonocatalytic method. A solvothermal procedure is used for doping, and the Cu- and Mn-doped ZnO nanocatalyst were characterized by means of FTIR, XRD, AFM, SEM, and EDAX analyses. We investigate the effect of operational variables, including doping ratio, initial pH, catalyst dose, initial HS content, and illuminance on the removal efficiency of the processes. The findings of the analyses used for the characterization of the nanoparticles illustrate the appropriate synthesis of the Cu- and Mn-doped ZnO nanocatalysts. We observe the highest removal efficiency rate under acidic conditions and the process efficiency decreased with increasing solution pH, when we tested it in the range of 3–7. Photocatalytic decomposition of HS increases with a rise in catalyst dose, but an increase in initial HS content results in decreasing the removal efficiency. We observe the highest photocatalytic degradation of humic acid while using the visible light, and the highest removal efficiency is obtained using Cu.ZnO. The Cu.ZnO also shows better performance under ultraviolet irradiation compared to other agents.
- ItemRemarkable performance recovery in highly defective perovskite solar cells by photo-oxidation(London [u.a.] : RSC, 2023) Goetz, Katelyn P.; Thome, Fabian T. F.; An, Qingzhi; Hofstetter, Yvonne J.; Schramm, Tim; Yangui, Aymen; Kiligaridis, Alexander; Loeffler, Markus; Taylor, Alexander D.; Scheblykin, Ivan G.; Vaynzof, YanaExposure to environmental factors is generally expected to cause degradation in perovskite films and solar cells. Herein, we show that films with certain defect profiles can display the opposite effect, healing upon exposure to oxygen under illumination. We tune the iodine content of methylammonium lead triiodide perovskite from understoichiometric to overstoichiometric and expose them to oxygen and light prior to the addition of the top layers of the device, thereby examining the defect dependence of their photooxidative response in the absence of storage-related chemical processes. The contrast between the photovoltaic properties of the cells with different defects is stark. Understoichiometric samples indeed degrade, demonstrating performance at 33% of their untreated counterparts, while stoichiometric samples maintain their performance levels. Surprisingly, overstoichiometric samples, which show low current density and strong reverse hysteresis when untreated, heal to maximum performance levels (the same as untreated, stoichiometric samples) upon the photooxidative treatment. A similar, albeit smaller-scale, effect is observed for triple cation and methylammonium-free compositions, demonstrating the general application of this treatment to state-of-the-art compositions. We examine the reasons behind this response by a suite of characterization techniques, finding that the performance changes coincide with microstructural decay at the crystal surface, reorientation of the bulk crystal structure for the understoichiometric cells, and a decrease in the iodine-to-lead ratio of all films. These results indicate that defect engineering is a powerful tool to manipulate the stability of perovskite solar cells.
- ItemPolycapillary-boosted instrument performance in the extreme ultraviolet regime for inverse photoemission spectroscopy(Washington, DC : Optica, 2017) Braig, Christoph; Sokolov, Andrey; Wilks, Regan G.; Kozina, Xeniya; Kunze, Thomas; Bjeoumikhova, Sempfira; Thiel, Markus; Erko, Alexei; Bär, MarcusA collimating polycapillary half lens, traditionally used in the medium and hard X-ray band, is operated at a photon energy of 36 eV for the first time. While the transmission still exceeds 50%, the measured and simulated spatial resolution and angular divergence approach 0.4 mm or less and at most 20 mrad, respectively. This unexpected, superior performance of the polycapillary optic in the extreme Ultraviolet could enable the design of an e cient, versatile and compact spectrometer for inverse photoemission spectroscopy (IPES): Its wavelength-dispersive component, a customized reflection zone plate, can maintain an energy resolution of 0.3 eV, whereas the sensitivity may be enhanced by more than one order of magnitude, compared to conventional spectrometers. Furthermore, the overall length of 0.9 m would allow for an eased alignment and evacuation. We see a significant potential for numerous polycapillary-based XUV / soft X-ray instruments in the future, in particular after further optimization for this long wavelength regime.
- ItemThree-Dimensional Cobalt Hydroxide Hollow Cube/Vertical Nanosheets with High Desalination Capacity and Long-Term Performance Stability in Capacitive Deionization([Beijing] : China Association for Science and Technology, 2021) Xiong, Yuecheng; Yu, Fei; Arnold, Stefanie; Wang, Lei; Presser, Volker; Ren, Yifan; Ma, JieFaradaic electrode materials have significantly improved the performance of membrane capacitive deionization, which offers an opportunity to produce freshwater from seawater or brackish water in an energy-efficient way. However, Faradaic materials hold the drawbacks of slow desalination rate due to the intrinsic low ion diffusion kinetics and inferior stability arising from the volume expansion during ion intercalation, impeding the engineering application of capacitive deionization. Herein, a pseudocapacitive material with hollow architecture was prepared via template-etching method, namely, cuboid cobalt hydroxide, with fast desalination rate (3.3 mg (NaCl)·g-1 (h-Co(OH)2)·min-1 at 100 mA·g-1) and outstanding stability (90% capacity retention after 100 cycles). The hollow structure enables swift ion transport inside the material and keeps the electrode intact by alleviating the stress induced from volume expansion during the ion capture process, which is corroborated well by in situ electrochemical dilatometry and finite element simulation. Additionally, benefiting from the elimination of unreacted bulk material and vertical cobalt hydroxide nanosheets on the exterior surface, the synthesized material provides a high desalination capacity ( mg (NaCl)·g-1 (h-Co(OH)2) at 30 mA·g-1). This work provides a new strategy, constructing microscale hollow faradic configuration, to further boost the desalination performance of Faradaic materials.
- ItemIntermolecular charge transfer enhances the performance of molecular rectifiers(Washington, DC [u.a.] : Assoc., 2022) Sullivan, Ryan P.; Morningstar, John T.; Castellanos-Trejo, Eduardo; Bradford, Robert W.; Hofstetter, Yvonne J.; Vaynzof, Yana; Welker, Mark E.; Jurchescu, Oana D.Molecular-scale diodes made from self-assembled monolayers (SAMs) could complement silicon-based technologies with smaller, cheaper, and more versatile devices. However, advancement of this emerging technology is limited by insufficient electronic performance exhibited by the molecular current rectifiers. We overcome this barrier by exploiting the charge-transfer state that results from co-assembling SAMs of molecules with strong electron donor and acceptor termini. We obtain a substantial enhancement in current rectification, which correlates with the degree of charge transfer, as confirmed by several complementary techniques. These findings provide a previously enexplored method for manipulating the properties of molecular electronic devices by exploiting donor/acceptor interactions. They also serve as a model test platform for the study of doping mechanisms in organic systems. Our devices have the potential for fast widespread adoption due to their low-cost processing and self-assembly onto silicon substrates, which could allow seamless integration with current technologies.