Impact of light scattering for efficiency enhancement in organic solar cells

Further efficiency enhancements in organic solar cells require a deeper understanding of the charge generation and transport in the cell as well as the employment of advanced light trapping mechanisms. Both electronic and optical device models for organic solar cells have been developed already in the past. This paper, however, for the first time presents a simulation tool that combines a state of the art driftdiffusion electrical model with a complex optical model able to simulate wave propagation in thin film optics but also ray-based light propagation in incoherent layers and scalar scattering. The combination of the light-scattering algorithm and this driftdiffusion model leads to a coupled opto-electronic cell model which represents a powerful design tool for cell characterization and optimization. This tool is then used to evaluate the gain of efficiency introduced by a light scattering interface made of a rough TCO in a bulk heterojunction (BHJ) solar cell. The results were found to be in good qualitative agreement with previously published experimental results

Evolutionary optimization of TCO/mesh electrical contacts in CIGS solar cells

State of the art solar cells often require a combination of TCO and metallic grid to efficiently transport the generated current to an external circuit. Optimization of these complex contacts based on several materials with different conductivities and geometries is often still based on a traditional approach consisting of simple analytical formulas and empirical knowledge in spite of the complexity. An evolutionary algorithm combined with an electrical 2D+1D FEM model is used to optimize the shape of the metallic contact considering the material conductivities, the geometry and shadowing. The performance of two automatically designed contacts is compared with experimental results of CIGS solar cells prepared with two different TCO thicknesses

Electrothermal Finite-Element Modeling for Defect Characterization in Thin-Film Silicon Solar Modules

We present and validate a finite-element model for coupled charge and heat transport in monolithically interconnected thin-film solar modules. Using measured current-voltage (I-V) and lock-in thermography (LIT) measurements of amorphous silicon minimodules, we experimentally validate our model. The entire module volume is represented by two planes (front and back electrodes) which are coupled in vertical direction using 1-D models, leading to a large reduction of the degrees of freedom in the numerical model and contributing to an efficient solution approach. As compared to 3-D models, the vertical coupling of the charge transport is represented by local temperature-dependent I-V curves. These can be obtained by drift-diffusion calculations, single-cell measurements or, as presented here, by an analytical solar cell diode model. Inhomogeneous heat sources such as Joule's heating in the electrodes lead to nonuniform temperature distributions. The explicit temperature dependence in the local I-V curve, therefore, mediates the feedback of the thermal transport on the local electrical cell characteristics. We employ measured I-V curves under partial illumination and analytical solutions for the potential distribution to validate this approach. Further, with LIT measurements of the same modules with and without artificially induced electrical shunts, we verify the computed temperature distributions

Simulations, measurements and optimization of OLEDs with scattering layer

A multi-scale optical model for organic light-emitting devices containing scattering layers is presented. This model describes the radiation of embedded oscillating dipoles and scattering from spherical particles. After successful model validation with experiments on a top-emitting white OLED, we show how this tool can be used for optimization with specific targets

Extended light scattering model incorporating coherence for thin-film silicon solar cells

We present a comprehensive scalar light-scattering model for the optical simulation of silicon thin film solar cells. The model integrates coherent light propagation in thin layers with a direct, noniterative treatment of light scattered at rough layer interfaces. The direct solution approach ensures computational efficiency, which is a key advantage for extensive calculations in the context of evaluation of different cell designs and parameter extraction. We validate the model with experimental external quantum efficiency spectra of state-of-the-art microcrystalline silicon solar cells. The simulations agree very well with measurements for cells deposited on both rough and flat substrates. The model is then applied to study the influence of the absorber layer thickness on the maximum achievable photocurrent for the two cell types. This efficient numerical framework will enable a quantitative model-based assessment of the optimization potential for light trapping in textured thin film silicon solar cells

Limited predictive value of FDG-PET for response assessment in the preoperative treatment of esophageal cancer : results of a prospective multi-center trial (SAKK 75/02)

BACKGROUND: Only responding patients benefit from preoperative therapy for locally advanced esophageal carcinoma. Early detection of non-responders may avoid futile treatment and delayed surgery. PATIENTS AND METHODS: In a multi-center phase ll trial, patients with resectable, locally advanced esophageal carcinoma were treated with 2 cycles of induction chemotherapy followed by chemoradiotherapy (CRT) and surgery. Positron emission tomography with 2[fluorine-18]fluoro-2-deoxy-d-glucose (FDG-PET) was performed at baseline and after induction chemotherapy. The metabolic response was correlated with tumor regression grade (TRG). A decrease in FDG tumor uptake of less than 40% was prospectively hypothesized as a predictor for histopathological non-response (TRG < 2) after CRT. RESULTS: 45 patients were included. The median decrease in FDG tumor uptake after chemotherapy correlated well with TRG after completion of CRT (p = 0.021). For an individual patient, less than 40% decrease in FDG tumor uptake after induction chemotherapy predicted histopathological non-response after completion of CRT, with a sensitivity of 68% and a specificity of 52% (positive predictive value 58%, negative predictive value 63%). CONCLUSIONS: Metabolic response correlated with histopathology after preoperative therapy. However, FDG-PET did not predict non-response after induction chemotherapy with sufficient clinical accuracy to justify withdrawal of subsequent CRT and selection of patients to proceed directly to surgery

Team functioning across different tumour types: Insights from a Swiss cancer center using qualitative and quantitative methods.

BACKGROUND: Multidisciplinary care is pivotal in cancer centres and the interaction of all cancer disease specialists in decision making processes is state-of-the-art. AIM: To describe differences of MDTMs by tumour type. METHODS: Twelve multidisciplinary team meetings (MDTMs) with participation of different cancer disease specialists at a tertiary hospital were assessed by an exploratory sequential mixed method approach with interviews, observations and a survey to address the following five topics: organisational structure and supporting technology; leadership; teamwork; decision-making, perceived value and motivation. Thirteen persons with different tumour specialities and levels of seniority were interviewed. The 12 MDTMs were observed twice by uninvolved persons and evaluated by the participating physicians with a survey. RESULTS: There were no systematic differences between MDTMs for different tumour types with the exception of the non-disease specific type MDTM, which was the only one for which the organisational structure was not driven by an electronic tool. However, several factors could be identified that generally influenced the functioning of the MDTMs. In particular, the quality of decision-making was highly dependent on the availability of case-based information and the presence of relevant cancer disease specialists. Leadership and teamwork were rated as important and were comparable across the MDTM. Team participants' motivation and perceived value of MDTMs was high across all meetings. CONCLUSION: MDTM at a single institution did not demonstrate disease specific characteristics. An effective MDTM, irrespective of the tumour type, can be successfully structured by technical means and a chairperson coordinating the interaction of cancer disease specialists to improve the decision-making process

Oncological care organisation during COVID-19 outbreak

Funding: This work was supported by Fonds de la Recherche Scientifique (grant to CEO) and Fondation Léon Fredericq (grant to GJ and CEO).Background: COVID-19 appeared in late 2019, causing a pandemic spread. This led to a reorganisation of oncology care in order to reduce the risk of spreading infection between patients and healthcare staff. Here we analysed measures taken in major oncological units in Europe and the USA. Methods: A 46-item survey was sent by email to representatives of 30 oncological centres in 12 of the most affected countries. The survey inquired about preventive measures established to reduce virus spread, patient education and processes employed for risk reduction in each oncological unit. Results: Investigators from 21 centres in 10 countries answered the survey between 10 April and 6 May 2020. A triage for patients with cancer before hospital or clinic visits was conducted by 90.5% of centres before consultations, 95.2% before day care admissions and in 100% of the cases before overnight hospitalisation by means of phone calls, interactive online platforms, swab test and/or chest CT scan. Permission for caregivers to attend clinic visits was limited in many centres, with some exceptions (ie, for non-autonomous patients, in the case of a new diagnosis, when bad news was expected and for terminally ill patients). With a variable delay period, the use of personal protective equipment was unanimously mandatory, and in many centres, only targeted clinical and instrumental examinations were performed. Telemedicine was implemented in 76.2% of the centres. Separated pathways for COVID-19-positive and COVID-19-negative patients were organised, with separate inpatient units and day care areas. Self-isolation was required for COVID-19-positive or symptomatic staff, while return to work policies required a negative swab test in 76.2% of the centres. Conclusion: Many pragmatic measures have been quickly implemented to deal with the health emergency linked to COVID-19, although the relative efficacy of each intervention should be further analysed in large observational studies

Oesophageal cancer: Exploring controversies overview of experts' opinions of Austria, Germany, France, Netherlands and Switzerland

Background: Oesophageal carcinoma is a rare disease with often dismal prognosis. Despite multiple trials addressing specific issues, currently, many questions in management remain unanswered. This work aimed to specifically address areas in the management of oesophageal cancer where high level evidence is not available, performing trials is very demanding and for many questions high-level evidence will not be available in the forseeable future. Methods: Two experts of each national, oesophageal cancer research group from Austria, France, Germany, the Netherlands and Switzerland were asked to provide statements to controversial issues. After an initial survey, further questions were formulated and answered by all experts. The answers were then discussed and qualitatively analysed for consensus and controversy. Results: Topics such as indications for PET-CT, reasons for induction chemotherapy, radiotherapy dose, the choice of definitive chemo-radiotherapy versus surgery in squamous cell cancer, the role of radiotherapy in adenocarcinoma and selected surgical issues were identified as topics of interest and discussed. Conclusion: Areas of significant controversy exist in the management of oesophageal cancer, mostly due to high-level evidence. This is not expected to change in the upcoming years