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Wenjun Xiang

Publications and source records attributed to Wenjun Xiang.

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Thermal Corrections and Analysis on the Phase Stability of CsPbCl3 and Cs2AgSbCl6 during In-Situ Thermal Treatment

Cesium lead chloride (CsPbCl3) is a well known and principal model for inorganic perovskite halide optoelectronic research. The many available techniques including high temperature stability testing have been used to investigate the increasing interest in inorganic perovskites as primary layers in solar cell applications. Due to the nature of high temperature testing, the characterization technique, reproducibility, and the true sample temperature are vital in determining relative stability. By choosing CsPbCl3 in the investigation of the structural stability of perovskites at high temperatures, it acts as a baseline to create and verify a methodology that accurately probes sample temperature, phase transitions, and decomposition onsets. Therefore, we present a methodological approach to investigate the thermal interactions and stability of CsPbCl3 as a parent single perovskite halide based on ligand-assisted re-precipitation synthesis techniques. Where we use our approach to inform and probe thermal interactions in other cesium/chlorine compounds like Cs2AgSbCl6. By analyzing the stoichiometry and initial phases through investigations of the crystalline structure and particle morphology, we calculated temperature conversions using a control substrate and refinements to best estimate changing structure parameters. Using in-situ temperature dependent X-ray diffraction, we were able to effectively probe the phase transitions and decomposition temperatures of the investigated halide powders. Creating a process that can confirm known high temperature structural phenomena of model perovskite halides while verifying our true sample temperature. Which allowed for further testing on the thermal kinetics of on the double perovskite structure Cs2AgSbCl6 and will continue to allow us to test other perovskites and perovskite families of interest in modern high temperature perovskite halide research.

cond-mat.mtrl-sci

Graphene Aerogel Ink for the Inkjet Printing of the Micro-Supercapacitors

The advances in the mass scale manufacturing of microscale energy storage devices via inkjet printing rely on the development of high-quality printable ink. The earth-abundant, non-toxic carbon materials such as graphene, carbon nanotube (CNT), reduced graphene oxide (r-GO) have shown excellent electrochemical performance and thus garnered significant interest as suitable electrode material. Here we report the formulation of printable graphene aerogel ink and the fabrication of the micro-supercapacitors (μ-SCs) on flexible polyimide substrates via inkjet printing method. The advantage of using pristine graphene aerogel intends to avoid the complex processing steps and the use of toxic chemicals in the ink formulation and lower the concentration of other additive components. Thus, a higher loading of active functional material in the printable ink is achieved. The aerogel ink directly employed to write the interdigitated μ-SCs devices on a flexible polyimide substrate at room temperature via inkjet printing. The electrochemical performance measured using the organic ionic liquid in the voltage range of 0-1 volt. These printed μ-SCs showed an areal capacity of 55 μF/cm2 at a current density of 6 micro-amp/cm2. The printed devices showed good stability, with ~80% of capacity retention after 10,000 cycles. Contrary to the graphene-based μ-SCs, the aerogel micro-supercapacitors do not show a significant distortion in the CV scan even at a very high scan rate of ~2Vs-1. Thus, we propose graphene aerogel as promising electrode material for mass-scale production of the μ-SCs.

physics.app-ph