Nanocarbon-Based photovoltaics

Carbon materials are excellent candidates for photovoltaic solar cells: they are Earth-abundant, possess high optical absorption, and superior thermal and photostability. Here we report on solar cells with active layers made solely of carbon nanomaterials that present the same advantages of conjugated polymer-based solar cells - namely solution processable, potentially flexible, and chemically tunable - but with significantly increased photostability and the possibility to revert photodegradation. The device active layer composition is optimized using ab-initio density functional theory calculations to predict type-II band alignment and Schottky barrier formation. The best device fabricated is composed of PC70BM fullerene, semiconducting single-walled carbon nanotubes and reduced graphene oxide. It achieves a power conversion efficiency of 1.3% - a record for solar cells based on carbon as the active material - and shows significantly improved lifetime than a polymer-based device. We calculate efficiency limits of up to 13% for the devices fabricated in this work, comparable to those predicted for polymer solar cells. There is great promise for improving carbon-based solar cells considering the novelty of this type of device, the superior photostability, and the availability of a large number of carbon materials with yet untapped potential for photovoltaics. Our results indicate a new strategy for efficient carbon-based, solution-processable, thin film, photostable solar cells

The sac evolution imaging follow-up after endovascular aortic repair: An international expert opinion-based Delphi consensus study

Objective: Management of follow-up protocols after endovascular aortic repair (EVAR) varies significantly between centers and is not standardized according to sac regression. By designing an international expert-based Delphi consensus, the study aimed to create recommendations on follow-up after EVAR according to sac evolution. Methods: Eight facilitators created appropriate statements regarding the study topic that were voted, using a 4-point Likert scale, by a selected panel of international experts using a three-round modified Delphi consensus process. Based on the experts’ responses, only those statements reaching a grade A (full agreement $75$80% and full disagreement <5%) were included in the final document. Results: One-hundred and seventy-four participants were included in the final analysis, and each voted the initial 29 statements related to the definition of sac regression (Q1-Q9), EVAR follow-up (Q10-Q14), and the assessment and role of sac regression during follow-up (Q15-Q29). At the end of the process, 2 statements (6.9%) were rejected, 9 statements (31%) received a grade B consensus strength, and 18 (62.1%) reached a grade A consensus strength. Of 27 final statements, 15 (55.6%) were classified as grade I, whereas 12 (44.4%) were classified as grade II. Experts agreed that sac regression should be considered an important indicator of EVAR success and always be assessed during follow-up after EVAR. Conclusions: Based on the elevated strength and high consistency of this international expert-based Delphi consensus, most of the statements might guide the current clinical management of follow-up after EVAR according to the sac regression. Future studies are needed to clarify debated issues. (J Vasc Surg 2024;80:937-45.

A Retrospective Analysis of Biological Complications of Dental Implants

Background and Objective. Several risk factors have been implicated in onset and development of peri-implant diseases. The impact of these factors, however, remains controversial across the different clinical settings and populations. The aim of this retrospective study was to evaluate the risk factors for peri-implant diseases among an Emirati population. Methods. A retrospective analysis of patients aged ≥18 years and having dental implants placed at Dubai Health Authority in 2010. Relevant information related to systemic-, patient-, implant-, site-, surgical- and prosthesis-related factors were collected. The strength of association between the prevalence of peri-implant mucositis and peri-implantitis and each variable was measured by chi-square analysis. A binary logistic regression analysis was performed to identify possible risk factors. Results. A total of 162 patients with 301 implant-supported restorations were included in the study. The age of the patients ranged between 19 and 72 with a mean age of 46.4 ± 11.7 years. The prevalence of peri-implant mucositis at the patient and implant levels were 44.4% and 38.2%, respectively. For peri-implantitis, the prevalence at the patient level was 5.6%, while the prevalence at the implant level was 4.0%. The binary logistic regression identified three risk factors (smoking habits, histories of treated periodontitis and lack of peri-implant maintenance) for peri-implantitis. Conclusion. Within the limitations of this study, smoking habits, history of treated periodontitis and lack of peri-implant maintenance were significant risk factors for peri-implantitis. Early detection of these factors would ensure appropriate planning and care of patients at high risk of developing peri-implant diseases. © 2022 Momen A. Atieh et al.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Folded-Light-Path Colloidal Quantum Dot Solar Cells SUBJECT AREAS: NANOPARTICLES APPLIED OPTICS ELECTRICAL AND ELECTRONIC ENGINEERING SOLAR CELLS

Colloidal quantum dot photovoltaics combine low-cost solution processing with quantum size-effect tuning to match absorption to the solar spectrum. Rapid advances have led to certified solar power conversion efficiencies of over 7%. Nevertheless, these devices remain held back by a compromise in the choice of quantum dot film thickness, balancing on the one hand the need to maximize photon absorption, mandating a thicker film, and, on the other, the need for efficient carrier extraction, a consideration that limits film thickness. Here we report an architecture that breaks this compromise by folding the path of light propagating in the colloidal quantum dot solid. Using this method, we achieve a substantial increase in short-circuit current, ultimately leading to improved power conversion efficiency. S olution-processed solar cells offer the promise of low cost, large-area processing, and, prospectively, high solar power conversion efficiencies Results In the present work, we sought to increase the interaction of light with the absorbing CQD medium by passing light through the CQD layer multiple times. Multi-pass optical management shemes have been shown to be effective in crystalline silicon We sought to assess quantitatively the extent to which the FLP strategy could enhance absorption, hence current. We began by exploring the spectral behaviour in the case of a 45u tilt angle. We show in The contribution of the additional passes through the CQD layer translates into added photon current through spectral multiplication with the AM 1.5 solar photon fluence spectrum 2

Influences of the neighbourhood food environment on adiposity of low-income preschool-aged children in Los Angeles County: a longitudinal study

BACKGROUND: Few studies have examined the association between the food environment and adiposity in early childhood, a critical time for obesity prevention. The objective of this study was to examine the longitudinal association between neighborhood food environment and adiposity among low-income preschool-aged children in a major metropolitan region in the United States. METHODS: The study sample was 32,172 low-income preschool-aged children in Los Angeles County who had repeated weight and height measurements collected between ages 2 and 5 years through a federal nutrition assistance program. We conducted multilevel longitudinal analyses to examine how spatial densities of healthy and unhealthy retail food outlets in the children’s neighborhoods were related to adiposity, as measured by weight-for-height z-score (WHZ), while controlling for neighborhood-level income and education, family income, maternal education, and child’s gender and race/ethnicity. RESULTS: Density of healthy food outlets was associated with mean WHZ at age 3 in a non-linear fashion, with mean WHZ being lowest for those exposed to approximately 0.7 healthy food outlets per square mile and higher for lesser and greater densities. Density of unhealthy food outlets was not associated with child WHZ. CONCLUSIONS: We found a non-linear relationship between WHZ and density of healthy food outlets. Research aiming to understand the socio-behavioral mechanisms by which the retail food environment influences early childhood obesity development is complex and must consider contextual settings