9,633 research outputs found
Energy barrier at the N719-dye/CsSnI3 interface for photogenerated holes in dye-sensitized solar cells
This report is to address the question if black γ-polymorph of cesium tin tri-iodide (B-γ-CsSnI3) can be used as a solid-state hole-transport material in the conventional DSSCs with the N719 dye to replace the liquid electrolyte as reported by I. Chung et al. on Nature 485, 486, (2012). Here we demonstrate rigorously that B-γ-CsSnI3 is not energetically possible to collect photogenerated holes because of the large energy barrier at the interface of N719/B-γ-CsSnI3. Therefore, it cannot serve as a hole-transporter for the conventional DSSCs although it is a good hole-conducting material. A solution-based method was employed to synthesize the B-γ-CsSnI3 polycrystalline thin-films used for this work. These thin-films were then characterized by X-ray diffraction, Hall measurements, optical reflection, and photoluminescence (PL). Particularly, spatially resolved PL intensity images were taken after B-γ-CsSnI3 was incorporated in the DSSC structure to insure the material integrity. The means of ultraviolet photoemission spectroscopy (UPS) was used to reveal why B-γ-CsSnI3 could not act as the substitute of liquid electrolyte in the conventional DSSCs. For the completeness, other two related compounds, one is the yellow polymorph of CsSnI3 and other is Cs2SnI6 with tetravalent tin instead of double-valent tin in CsSnI3 were also investigated by UPS
Multi-Objective Ant Colony Algorithm in EPC Risk Control
AbstractAccording to the risks and risk control target in energy performance contracting (EPC), this paper has designed the risk control measure set. On the basis, a risk control model is put forward, including the risk evaluation, risk control cost, risk loss. Then, a multi-objective ant colony algorithm, based on Pareto theory, is used to solve the model. A series of Pareto optimal solutions are got by example. The result shows that the solutions have the better diversity and convergence. At the same time, the model can find the best combination of various risk control measures in EPC, which can provide direct evidence for the company of EPC
Dynamics of quantum coherence in many-body localized systems
We demonstrate that the dynamics of quantum coherence serves as an effective
probe for identifying dephasing, which is a distinctive signature of many-body
localization (MBL). Quantum coherence can be utilized to measure both the local
coherence of specific subsystems and the total coherence of the whole system in
a consistent manner. Our results reveal that the local coherence of small
subsystems decays over time following a power law in the MBL phase, while it
reaches a stable value within the same time window in the Anderson localized
(AL) phase. In contrast, the total coherence of the whole system exhibits
logarithmic growth during the MBL phase and reaches a stable value in the AL
phase. Notably, this dynamic characteristic of quantum coherence remains robust
even with weak interactions and displays unbounded behavior in infinite
systems. Our results provide insights into understanding many-body dephasing
phenomena in MBL systems and propose a novel feasible method for identifying
and characterizing MBL phases in experiments
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