Critical slowing down of the charge carrier dynamics at the Mott metal-insulator transition.

We report on the dramatic slowing down of the charge carrier dynamics in a quasi-two-dimensional organic conductor, which can be reversibly tuned through the Mott metal-insulator transition (MIT). At the finite-temperature critical end point, we observe a divergent increase of the resistance fluctuations accompanied by a drastic shift of spectral weight to low frequencies, demonstrating the critical slowing down of the order parameter (doublon density) fluctuations. The slow dynamics is accompanied by non-Gaussian fluctuations, indicative of correlated charge carrier dynamics. A possible explanation is a glassy freezing of the electronic system as a precursor of the Mott MIT.

Local Enhancement of Dopant Diffusion from Polycrystalline Silicon Passivating Contacts.

Passivating contacts consisting of heavily doped polycrystalline silicon (poly-Si) and ultrathin interfacial silicon oxide (SiOx) films enable the fabrication of high-efficiency Si solar cells. The electrical properties and working mechanism of such poly-Si passivating contacts depend on the distribution of dopants at their interface with the underlying Si substrate of solar cells. Therefore, this distribution, particularly in the vicinity of pinholes in the SiOx film, is investigated in this work. Technology computer-aided design (TCAD) simulations were performed to study the diffusion of dopants, both phosphorus (P) and boron (B), from the poly-Si film into the Si substrate during the annealing process typically applied to poly-Si passivating contacts. The simulated 2D doping profiles indicate enhanced diffusion under pinholes, yielding deeper semicircular regions of increased doping compared to regions far removed from the pinholes. Such regions with locally enhanced doping were also experimentally demonstrated using high-resolution (5-10 nm/pixel) scanning spreading resistance microscopy (SSRM) for the first time. The SSRM measurements were performed on a variety of poly-Si passivating contacts, fabricated using different approaches by multiple research institutes, and the regions of doping enhancement were detected on samples where the presence of pinholes had been reported in the related literature. These findings can contribute to a better understanding, more accurate modeling, and optimization of poly-Si passivating contacts, which are increasingly being introduced in the mass production of Si solar cells.

The workplace impact of acute exacerbations of chronic bronchitis (AECB); A literature review.

Acute exacerbations of chronic bronchitis (AECB) are known to have a substantial economic burden in terms of medical care costs. The objective of this study was to assess workplace-based costs associated with AECB, including absenteeism and decreased productivity, based on a review of published literature. A secondary goal was to identify factors related to workplace-based costs in AECB. A literature search was conducted to identify relevant articles assessing one or more aspects of work loss or workplace costs among patients with chronic bronchitis. A review of the identified literature indicates that patients with chronic bronchitis had more days off work; patients whose exacerbations were treated were less likely to have additional exacerbations and had comparatively less work loss. Findings suggest that clinical outcomes and workplace costs are related. While this relationship is clearer in terms of work loss, further exploration is needed to assess decreased productivity and to evaluate this relationship using objective indicators of absenteeism and productivity rather than recall.