Characterization and loss analyses of passivated emitter and rear cells

This work presents characterization methods and simulation-based loss analyses for passivated emitter and rear (PERC) solar cells. Furthermore, it discusses possible ways of introducing poly-Si on thin inter-facial oxides (POLO) junctions into industrial solar cells. Achieving a further efficiency increase of industrial \gls{PERC} cells is becoming more and more difficult because the margin to the theoretical limit is reduced step by step. Identifying the major loss channel in terms of a potential efficiency gain, thus, plays an increasingly important role in solar cell optimization. The free energy loss analysis (FELA) and the synergistic efficiency gain analysis (SEGA) as simulation-based loss analyses can address this task. The basis for both the FELA and the SEGA are numerical device simulations based on experimentally determined input parameters. The determination of most of these input parameters can be achieved with measurement and data analysis tools, which are commonly used in PV-research. The recombination at local metal contacts, however, has not been studied to the same extent and standard techniques do not apply. In this work, we study the determination of contact recombination parameters. We first analyze the required sample structures and develop an analytical model to calculate the length scale on which regions of different charge carrier lifetimes affect each other. We find that a metallization pattern with three metallized and one non-metallized quarters fits our requirements best. In the analysis of suitable measurement setups we find that photoconductance-calibrated photoluminescence imaging is best suited because of the low uncertainty. For the extraction of contact recombination parameters we study the analytical model by Fischer and find an excellent agreement of better than 5% deviation with numerical device simulations, provided the assumptions of low level injection and either full line or periodic point contacts are fulfilled. For arbitrary contact layouts and for the full injection dependence we introduce an approach based on numerical device simulations. In this context, we develop a new model for injection dependent contact recombination currents. The model is based on the superposition of recombination at the Si-metal interface and within the highly doped layer underneath. We use standard measurement and evaluation techniques and determine contact recombination parameters to perform a complete characterization of a PERC cell batch. In this characterization we determine all input parameters required for a SEGA along with the respective uncertainties. From the uncertainties of the input parameters we determine the uncertainties of the SEGA results using a Monte-Carlo simulation. We also analyze the differences between SEGA and FELA and introduce a graphical user interface for automatic SEGA simulations. Finally we discuss different cell structures for integrating POLO junctions into industrial solar cells by means of SEGA simulations and hypothetical process flows. We identify cells featuring conventional screen-printed Al base contacts and n-type POLO (n-POLO) junctions as promising candidates for industrial integration in the near future. A further development step are solar cells with POLO junctions for both polarities, which show an absolute efficiency benefit between 0.3% and 0.4% compared to similar cells with Al base contacts. However, further research in structuring POLO layers and screen-printed contacting of p-type POLO (p-POLO) is required. From the SEGA simulations and the hypothetical process flows a cell development roadmap was derived, in order to focus research activities on the most promising cell concepts

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

How to reveal metastable skyrmionic spin structures by spin-polarized scanning tunneling microscopy

We predict the occurrence of metastable skyrmionic spin structures such as antiskyrmions and higher-order skyrmions in ultra-thin transition-metal films at surfaces using Monte Carlo simulations based on a spin Hamiltonian parametrized from density functional theory calculations. We show that such spin structures will appear with a similar contrast in spin-polarized scanning tunneling microscopy (SP-STM) images. Both skyrmions and antiskyrmions display a circular shape for out-of-plane magnetized tips and a two-lobe butterfly contrast for in-plane tips. An unambiguous distinction can be achieved by rotating the tip magnetization direction without requiring the information of all components of the magnetization

Fundmeldungen Neufunde – Bestätigungen – Verluste

Die Fundmeldungen in Band 34 von Botanik und Naturschutz in Hessen stammen von: Dirk Bönsel, Martin De Jong, Klaus Dühr, Uta Engel, Benjamin Feller, Christian Feuring, Thomas Gregor, Arthur Händler, Karsten Horn, Diemut Klärner, Julia Kruse, Eric Martiné, Hasko Friedrich Nesemann, Kai Uwe Nierbauer, Uwe Raabe, Susanne Raehse, Felix Reischmann, Bernd Sauerwein, Petra Schmidt, Fabian Schrauth, Christof Nikolaus Schröder, Helmut Siebert, Michael Thieme, Otto Wacker und Rüdiger Wittig