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Background: Platinum-based chemotherapy with cetuximab is the standard of care for relapsed or metastatic squamous cell carcinoma of the head and neck (SCCHN). The aim of this trial was to investigate whether cetuximab and paclitaxel/carboplatin can achieve similar progression-free survival (PFS) with standard cetuximab and 5-FU/platinum-based chemotherapy. Standard chemotherapy treatment for SCCHN is related to severe toxicity and new, less toxic regimens are needed. Methods: In this multicentre, randomized, controlled, phase 2 trial, 85 patients with relapsed or metastatic SCCHN were randomized in a 1:1 ratio to cetuximab and 5-FU/cisplatin or carboplatin (arm A) vs. cetuximab and paclitaxel/carboplatin (arm B). Eligibility criteria included age &ge, 18 years, Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0&ndash, 1, and adequate organ functions. The primary endpoint was to investigate whether PFS in arm B is significantly worse than PFS in arm A. Results: Median PFS in arm A was 4.37 months (95% CI: 2.9&ndash, 5.9 m) and 6.5 months (95% CI: 4.8&ndash, 8.2 m) in arm B, (p = 0.064). Median overall survival (OS) was 8.4 months (95% CI: 5.3&ndash, 11.5 m) in arm A and 10.2 months (95% CI: 5.4&ndash, 15 m) in arm B, (HR = 0.71, 95% CI: 0.43&ndash, 1.16). PFS HR for arm B was not significantly worse than arm A (HR = 0.65, 95% CI: 0.41&ndash, 1.03). Adverse events &ge, grade 3 were more frequent in arm A than arm B (60% vs. 40%, p = 0.034). Conclusion: Cetuximab and paclitaxel/carboplatin was found to have similar efficacy and less toxicity compared to cetuximab and 5-FU/cisplatin or carboplatin. The experimental arm is easier to administer rendering it a favorable alternative to standard therapy.

Purpose: To evaluate the effect of magnetic resonance (MR) imaging (MRI) geometric distortions on head and neck radiation therapy treatment planning (RTP) for an MRI-only RTP. We also assessed the potential benefits of patient-specific shimming to reduce the magnitude of MR distortions for a 3-T scanner. Methods and Materials: Using an in-house Matlab algorithm, shimming within entire imaging volumes and user-defined regions of interest were simulated. We deformed 21 patient computed tomography (CT) images with MR distortion fields (gradient nonlinearity and patient-induced susceptibility effects) to create distorted CT (dCT) images using bandwidths of 122 and 488 Hz/mm at 3 T. Field parameters from volumetric modulated arc therapy plans initially optimized on dCT data sets were transferred to CT data to compute a new plan. Both plans were compared to determine the impact of distortions on dose distributions. Results: Shimming across entire patient volumes decreased the percentage of voxels with distortions of more than 2 mm from 15.4% to 2.0%. Using the user-defined region of interest (ROI) shimming strategy, (here the Planning target volume (PTV) was the chosen ROI volume) led to increased geometric for volumes outside the PTV, as such voxels within the spinal cord with geometric shifts above 2 mm increased from 11.5% to 32.3%. The worst phantom-measured residual system distortions after 3-dimensional gradient nonlinearity correction within a radial distance of 200 mm from the isocenter was 2.17 mm. For all patients, voxels with distortion shifts of more than 2 mm resulting from patient-induced susceptibility effects were 15.4% and 0.0% using bandwidths of 122 Hz/mm and 488 Hz/mm at 3 T. Dose differences between dCT and CT treatment plans in D-50 at the planning target volume were 0.4% +/- 0.6% and 0.3% +/- 0.5% at 122 and 488 Hz/mm, respectively. Conclusions: The overall effect of MRI geometric distortions on data used for RTP was minimal. Shimming over entire imaging volumes decreased distortions, but user-defined subvolume shimming introduced significant errors in nearby organs and should probably be avoided.

Purpose: We describe a public dataset with MR and CT images of patients performed in the same position with both multiobserver and expert consensus delineations of relevant organs in the male pelvic region. The purpose was to provide means for training and validation of segmentation algorithms and methods to convert MR to CT like data, i.e., so called synthetic CT (sCT). Acquisition and validation methods: T1- and T2-weighted MR images as well as CT data were collected for 19 patients at three different departments. Five experts delineated nine organs for each patient based on the T2-weighted MR images. An automatic method was used to fuse the delineations. Starting from each fused delineation, a consensus delineation was agreed upon by the five experts for each organ and patient. Segmentation overlap between user delineations with respect to the consensus delineations was measured to describe the spread of the collected data. Finally, an open-source software was used to create deformation vector fields describing the relation between MR and CT images to further increase the usability of the dataset. Data format and usage notes: The dataset has been made publically available to be used for academic purposes, and can be accessed from . Potential applicationsThe dataset provides a useful source for training and validation of segmentation algorithms as well as methods to convert MR to CT-like data (sCT). To give some examples: The T2-weighted MR images with their consensus delineations can directly be used as a template in an existing atlas-based segmentation engine; the expert delineations are useful to validate the performance of a segmentation algorithm as they provide a way to measure variability among users which can be compared with the result of an automatic segmentation; and the pairwise deformably registered MR and CT images can be a source for an atlas-based sCT algorithm or for validation of sCT algorithm.

We study the interaction of electromagnetic waves in layered media with textured interfaces. Experimental results of a solar cell grown on a sinusoidal back reflector are compared with a theoretical model using an expansion into diffraction modes. We assume the validity of the Rayleigh hypothesis and show that the continuity equations extend the coupling only to neighboring orders for the case of sinusoidal textures. This approach includes all essential aspects of the coupling process and it requires only a moderate amount of mathematical complexity. Our modeling results correctly reproduce the absorption of the periodically textured solar cell for both polarization directions. The absorption phenomena underlying the light-trapping process can thus be studied with a small number of parameters like period, depth, and film thickness.

We investigate the angular behavior of the upper bound of absorption provided by the guided modes in thin film solar cells. We show that the 4n^2 limit can be potentially exceeded in a wide angular and wavelength range using two-dimensional periodic thin film structures. Two models are used to estimate the absorption enhancement; in the first one, we apply the periodicity condition along the thickness of the thin film structure but in the second one, we consider imperfect confinement of the wave to the device. To extract the guided modes, we use an automatized procedure which is established in this work. Through examples, we show that from the optical point of view, thin film structures have a high potential to be improved by changing their shape. Also, we discuss the nature of different optical resonances which can be potentially used to enhance light trapping in the solar cell. We investigate the two different polarization directions for one-dimensional gratings and we show that the transverse magnetic polarization can provide higher values of absorption enhancement. We also propose a way to reduce the angular dependence of the solar cell efficiency by the appropriate choice of periodic pattern. Finally, to get more practical values for the absorption enhancement, we consider the effect of parasitic loss which can significantly reduce the enhancement factor.

In this work a novel type of substrate for thin film silicon solar cells is studied. The substrate has the advantage of being physically flat to allow the growth of cells with excellent material quality while being optically rough for enhanced light trapping that leads to high short circuit current density. The substrate is made of rough zinc oxide (ZnO) which is grown on a flat silver reflector. The ZnO is then covered with amorphous silicon and the stack is polished to expose the tips of the pyramidal ZnO surface. The ZnO embedded in the amorphous matrix provides the desirable scattering of light while the surface onto which the cell is deposited is flat and allows for the growth of good quality material. We present results of ~4 µm thick microcrystalline silicon solar cells prepared on such substrates with high open circuit voltages of 520 mV. We also demonstrate a large relative efficiency gain of 10 compared to a state of the art cell which is grown directly on an optimized textured substrate. © 2012 Elsevier B.V. All rights reserved.

The challenge for all photovoltaic technologies is to maximize light absorption, to convert photons with minimal losses into electric charges, and to efficiently extract them to the electrical circuit. For thin-film solar cells, all these tasks rely heavily on the transparent front electrode. Here we present a multiscale electrode architecture that allows us to achieve efficiencies as high as 14.1% with a thin-film silicon tandem solar cell employing only 3 μm of silicon. Our approach combines the versatility of nanoimprint lithography, the unusually high carrier mobility of hydrogenated indium oxide (over 100 cm(2)/V/s), and the unequaled light-scattering properties of self-textured zinc oxide. A multiscale texture provides light trapping over a broad wavelength range while ensuring an optimum morphology for the growth of high-quality silicon layers. A conductive bilayer stack guarantees carrier extraction while minimizing parasitic absorption losses. The tunability accessible through such multiscale electrode architecture offers unprecedented possibilities to address the trade-off between cell optical and electrical performance.

Nanopatterning has gained tremendous importance in the field of photovoltaics, as absorption of sunlight in solar cells can be enhanced drastically by proper engineering of photonic nanostructures1– 8. However, despite intensive efforts, neither the ideal surface morphology nor the ideal scattering characteristics foroptimumlight trapping have been identified. Experimentally, a method capable of implementing arbitrarily designed surface morphologies directly into functional devices is desirable. Here, we establish a nanomoulding process that provides exactly such a platform, enabling precise, large-area, nanoscale patterning of functional zinc oxide films at low cost. We illustrate the application of nanomoulded zinc oxide films as transparent front electrodes in amorphous silicon solar cells, demonstrating excellent initial conversion efficiencies of 10.1%. In the quest to find the most efficient light-harvesting scheme, we anticipate that nanomoulding will catalyse the development and integration of exciting new nanophotonic structures.

We demonstrate high-efficiency thin-film silicon solar cells with transparent nanotextured front electrodes fabricated via ultraviolet nanoimprint lithography on glass substrates. By replicating the morphology of state-of-the-art nanotextured zinc oxide front electrodes known for their exceptional light trapping properties, conversion efficiencies of up to 12.0% are achieved for micromorph tandem junction cells. Excellent light incoupling results in a remarkable summed short-circuit current density of 25.9 mA/cm(2) for amorphous top cell and microcrystalline bottom cell thicknesses of only 250 and 1100 nm, respectively. As efforts to maximize light harvesting continue, our study validates nanoimprinting as a versatile tool to investigate nanophotonic effects of a large variety of nanostructures directly on device performance.

Elective treatment of lymph nodes in oropharyngeal cancer (OPC) has impact on both regional recurrences (RR) and risk of late side effects. This study was performed to quantify the dose-dependent impact on RR and overall survival (OS) in a prospectively collected cohort of OPC from the ARTSCAN study with emphasis on elective treatment. ARTSCAN is a previously published prospective, randomized, multicentre study of altered radiotherapy (RT) fractionation in head and neck cancer. In ARTSCAN the elective treatment volume for node positive OPC varied significantly between centres due to local treatment principles. All patients with OPC in complete response after primary treatment were eligible for the present case–control study. Cases were patients with RR during five years follow-up. Patients with no recurrence were eligible as controls. Four controls per case were matched according to T- and N-stage. Mean (D mean) and median (D 50%) dose for the lymph node level (LNL) of RR in the cases and the corresponding LNL in the controls were analysed with conditional logistic regression. OS was estimated with the Kaplan-Meier method and evaluated by multivariate Cox regression analysis. There was a dose-dependent risk reduction for D 50% in the interval that represented elective treatment (40–50 Gy) (OR = 0.18, p 60 Gy) did significantly worse (p

SWENOTECA has since 1998 offered patients with clinical stage I (CS I) nonseminoma, adjuvant chemotherapy with one course of bleomycin, etoposide and cisplatin (BEP). The aim has been to reduce the risk of relapse, sparing patients the need of toxic salvage treatment. Initial results on 312 patients treated with one course of adjuvant BEP, with a median follow-up of 4.5 years, have been previously published. We now report mature and expanded results.In a prospective, binational, population-based risk-adapted treatment protocol, 517 Norwegian and Swedish patients with CS I nonseminoma received one course of adjuvant BEP. Patients with lymphovascular invasion (LVI) in the primary testicular tumor were recommended one course of adjuvant BEP. Patients without LVI could choose between surveillance and one course of adjuvant BEP. Data for patients receiving one course of BEP are presented in this study.At a median follow-up of 7.9 years, 12 relapses have occurred, all with IGCCC good prognosis. The latest relapse occurred 3.3 years after adjuvant treatment. The relapse rate at 5 years was 3.2% for patients with LVI and 1.6% for patients without LVI. Five-year cause-specific survival was 100%.The updated and expanded results confirm a low relapse rate following one course of adjuvant BEP in CS I nonseminoma. One course of adjuvant BEP should be considered a standard treatment in CS I nonseminoma with LVI. For patients with CS I nonseminoma without LVI, one course of adjuvant BEP is also a treatment option.

Background: Weight loss is a common problem in patients with Squamous Cell Carcinoma of the Head and Neck (SCCHN) treated with radiotherapy (RT). The aims of the present study were to determine if treated volume (TV), as a measure of the radiation dose burden, can predict weight loss in patients with oropharyngeal cancer and to analyze weight loss and body mass index (BMI) in the same patient group in relation to 5-year overall survival. Methods: The ARTSCAN trial is a prospective, randomized, multicenter trial in patients with SCCHN. Nutritional data from the ARTSCAN trial were analyzed retrospectively using univariate and multivariate statistical methods based on information on percentage weight loss from the start of RT up to five months after the termination of RT (study cohort 1, n = 232) and information on patients' BMI at the start of RT (study cohort 2, n = 203). TV was defined as the volume of the patient receiving at least 95% of the prescribed dose. TV64.6 (Gy) encompasses macroscopic tumor and TV43.7 (Gy) elective lymph nodes of the neck. Results: TV64.6 Gy and TV43.7 Gy were both significantly correlated with higher weight loss up to five months after the termination of RT in study cohort 1 (p < 0.001 for both). BMI at the start of RT was shown to be a prognostic factor for 5-year overall survival in study cohort 2 but weight loss was not. The hazard ratios and 95% confidence intervals were 3.78 (1.46-9.75) and 2.57 (1.43-4.62) in patients with underweight and normal weight, respectively. Conclusions: TV can predict weight loss during RT in patients with oropharyngeal cancer regardless of clinical stage. A high BMI (>25 kg/m(2)) at the start of RT is positively associated with survival in patients with oropharyngeal cancer.

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

Background: The use of magnetic resonance (MR) imaging as a part of preparation for radiotherapy is increasing. For delineation of the prostate several publications have shown decreased delineation variability using MR compared to computed tomography (CT). The purpose of the present work was to investigate the intra- and inter-physician delineation variability for prostate and seminal vesicles, and to investigate the influence of different MR sequence settings used clinically at the five centers participating in the study. Methods: MR series from five centers, each providing five patients, were used. Two physicians from each center delineated the prostate and the seminal vesicles on each of the 25 image sets. The variability between the delineations was analyzed with respect to overall, intra-and inter-physician variability, and dependence between variability and origin of the MR images, i.e. the MR sequence used to acquire the data. Results: The intra-physician variability in different directions was between 1.3 - 1.9 mm and 3 - 4 mm for the prostate and seminal vesicles respectively (1 std). The inter-physician variability for different directions were between 0.7 - 1.7 mm and approximately equal for the prostate and seminal vesicles. Large differences in variability were observed for individual patients, and also for individual imaging sequences used at the different centers. There was however no indication of decreased variability with higher field strength. Conclusion: The overall delineation variability is larger for the seminal vesicles compared to the prostate, due to a larger intra-physician variability. The imaging sequence appears to have a large influence on the variability, even for different variants of the T2-weighted spin-echo based sequences, which were used by all centers in the study.

The aim of the present study was to evaluate the efficacy and safety of high-dose-rate brachytherapy alone or in combination with external pelvic irradiation in treatment of vaginal recurrences in endometrial carcinomas. Predictive and prognostic factors were also evaluated.Between 1990 and 2005, forty patients were consecutively treated for vaginal recurrences with or without extravaginal tumoral spread from endometrial carcinoma of International Federation of Gynecology and Obstetrics (FIGO) stages IA-IIIA. Thirty-five patients were treated primarily with surgery and five patients with primary radiotherapy. Six patients were treated with adjuvant external beam irradiation and seven patients with vaginal brachytherapy upfront. The medium time from diagnosis to recurrence was 17 months. The recurrences were treated with a combination of high-dose-rate brachytherapy (mean 25.8 Gy) and external beam pelvic irradiation (mean 46.7 Gy) in 24 cases (60%) and with external therapy-alone or brachytherapy-alone in 12 cases.The local control of vaginal recurrences treated with a combination of external beam therapy and brachytherapy was 92%. The local control rate was lower for external beam therapy-alone. In eleven patients (28%), a second recurrence occurred (five vaginal and six distant metastases). The overall 5-year survival rate was 50%. Age, FIGO grade and time from diagnosis to recurrence were the only independent and significant prognostic factors. Upfront external beam therapy was associated with a worse overall survival rate. Site of recurrence was significant only in univariate analysis. Late gastrointestinal toxicity (grade 3-4) was recorded in 11% of irradiated patients.Combined high-dose-rate brachytherapy and external beam therapy was an effective treatment for vaginal recurrences. Age, FIGO grade, and time-to-recurrence were significant and independent prognostic factors. Upfront radiotherapy was an unfavorable prognostic factor in univariate analysis.

Background In recent years, there has been a considerable research effort concerning the integration of magnetic resonance imaging (MRI) into the external radiotherapy workflow motivated by the superior soft tissue contrast as compared to computed tomography. Image registration is a necessary step in many applications, e.g. in patient positioning and therapy response assessment with repeated imaging. In this study, we investigate the dependence between the registration accuracy and the size of the registration volume for a subvolume based rigid registration protocol for MR images of the prostate. Methods Ten patients were imaged four times each over the course of radiotherapy treatment using a T2 weighted sequence. The images were registered to each other using a mean square distance metric and a step gradient optimizer for registration volumes of different sizes. The precision of the registrations was evaluated using the center of mass distance between the manually defined prostates in the registered images. The optimal size of the registration volume was determined by minimizing the standard deviation of these distances. Results We found that prostate position was most uncertain in the anterior-posterior (AP) direction using traditional full volume registration. The improvement in standard deviation of the mean center of mass distance between the prostate volumes using a registration volume optimized to the prostate was 3.9 mm (p < 0.001) in the AP direction. The optimum registration volume size was 0 mm margin added to the prostate gland as outlined in the first image series. Conclusions Repeated MR imaging of the prostate for therapy set-up or therapy assessment will both require high precision tissue registration. With a subvolume based registration the prostate registration uncertainty can be reduced down to the order of 1 mm (1 SD) compared to several millimeters for registration based on the whole pelvis.

Finding the optimal structure to enhance light trapping in thin film silicon solar cells has attracted much attention in the previous decades. However, because of problems in integrating theory and experiment, there are only few comprehensive contributions that provide guidelines for the optimal design of such structures. In this work, a realistic thin film solar cell with almost conformal layers based on a one-dimensional metallic grating back-reflector is investigated through experiment and theory. The external quantum efficiency of the cell is obtained with the aid of both theory and experiment for different angles of incidence and in both polarizations to validate the computational method and to show the impact of guided mode excitation. Different substrate shapes that are compatible with solar cell fabrication are then considered and the effect of geometrical parameters on the short circuit current density of the device is investigated. Calculations show that among the investigated shapes, trinagular gratings with a very sharp slope in one side, so called sawtooth gratings, are the most promising one-dimensional grating for light trapping. Furthermore, the role of material property is discussed specifically in the back-reflector by simulating aluminum and silver back-reflectors. It is shown that the blue response of the solar cells is similar almost regardless of the back-reflector material but their red response is viable to change due to variation in resonant properties of the structure.

Silver can be used as the back contact and reflector in thin film silicon solar cells. When deposited on textured substrates, silver films often exhibit reduced reflectance due to absorption losses by the excitation of surface plasmon resonances. We show that thermal annealing of the silver back reflector increases its reflectance drastically. The process is performed at low temperature (150°C) to allow the use of plastic sheets such as polyethylene naphthalate and increases the efficiency of single junction amorphous solar cells dramatically. We present the best result obtained on a flexible substrate: a cell with 9.9% initial efficiency and 15.82 mA/cm2 in short circuit current is realized in n-i-p configuration.

We investigate the influence of refractive index contrast on the light scattering properties of nanotextured interfaces, which serve as front contact for p-i-n thin-film silicon solar cells. We here focus on ZnO surfaces with randomly oriented pyramidal features, known for their excellent light trapping performance. Transparent replicas, with a different refractive index, but practically identical morphology compared to their ZnO masters, were fabricated via nanoimprinting. Within the theoretical framework we recently proposed, we show how the angular and spectral dependence of light scattered by nanostructures with identical morphology but different refractive index may be related to each other allowing direct comparison of their light trapping potential within the device.

Angle resolved measurements of the external quantum efficiency of a-Si solar cells deposited on a grating show strong absorption phenomena which are well explained with the guided mode structure in an equivalent flat multilayer system.

Squamous cell carcinoma antigen (SCCA) is a serological marker of squamous cell carcinomas (SCC). To study whether any of the SCCA isoforms would provide additional and more specific/sensitive clinical information than total SCCA, immunoassays specific for the different forms of SCCA (free SCCA2, total SCCA2, total SCCA1 and total SCCA) were developed. SCCA isoforms were determined before therapy and in follow-up samples from patients with cervical cancer and in serum samples from healthy females. Serum samples from patients with benign skin diseases (psoriasis and eczema) were also selected based on elevated SCCA levels. Rising levels of SCCA1 and SCCA2 were seen in patients with recurrence or progressive disease at the end of the study. The rise in SCCA2 was usually more prominent than that in SCCA1. The dominating serological form of SCCA was free SCCA2 both in healthy controls and in patients with cervical cancer. Both SCCA1 and SCCA2 were elevated in serum from cervical cancer patients and followed the clinical course of the disease during therapy monitoring. SCCA2 did not show improved tumor specificity as compared to SCCA1. A larger study is however necessary to make firm conclusions.

Several thin-film solar cell technologies require light-trapping schemes that are predominantly based on depositing the solar cells on rough surfaces. While this approach efficiently increases the density of photo-generated carriers, open-circuit voltage and fill factor generally decrease. Substrates that decouple the growth interface from the light-scattering interface were previously proposed as a solution to this dilemma, and proof-of-concepts were demonstrated in thin film-silicon solar cells. In this contribution, we review as an introduction the problematic of rough versus smooth interface for n-i-p single-junction lc-Si:H cells. Then, the benefits of the newly developed substrate that decouples the growth and scattering interfaces are investigated in n-i-p triple-junction a-Si:H/lc-Si:H/lc-Si:H solar cells for the first time. Conversion efficiencies of 13.7% (initial) and 12.5% (stabilized) are obtained, which are among the highest ever reported for such devices.

We investigate the performance of hydrogenated indium oxide as a transparent front electrode for micromorph thin-film silicon solar cells on glass. Light trapping is achieved by replicating the morphology of state-of-the-art zinc oxide electrodes, known for their outstanding light trapping properties, via ultraviolet nanoimprint lithography. As a result of the high electron mobility and excellent near-infrared transparency of hydrogenated indium oxide, the short-circuit current density of the cells is improved with respect to indium tin oxide and zinc oxide electrodes. We assess the potential for further current gains by identifying remaining sources of parasitic absorption and evaluate the light trapping capacity of each electrode. We further present a method, based on nonabsorbing insulating silicon nitride electrodes, allowing one to directly relate the optical reflectance to the external quantum efficiency. Our method provides a useful experimental tool to evaluate the light trapping potential of novel photonic nanostructures by a simple optical reflectance measurement, avoiding complications with electrical cell performance.

Despite the progress in the engineering of structures to enhance photocurrent in thin film solar cells, there are few comprehensive studies which provide general and intuitive insight into the problem of light trapping. Also, lack of theoretical propositions which are consistent with fabrication is an issue to be improved. We investigate a real thin film solar cell with almost conformal layers grown on a 1D grating metallic back-reflector both experimentally and theoretically. Photocurrent increase is observed as an outcome of guided mode excitation in both theory and experiment by obtaining the external quantum efficiency of the cell for different angles of incidence and in both polarization directions. Finally, the effect of geometrical parameters on the short circuit current density of the device is investigated by considering different substrate shapes that are compatible with solar cell fabrication. Based on our simulations, among the investigated shapes, triangular gratings with a very sharp slope in one side, so called sawtooth gratings, are the most promising 1D gratings for optimal light trapping.

We study the plasmonic and the non-plasmonic regimes of operation of a thin-film amorphous-silicon solar cell. By rigorous calculation, we discuss the impact of the cell geometry on the nature of its optical resonances.

We describe a method based on nanoimprinting and non-absorbing insulating silicon nitride electrodes for evaluating the light trapping potential of photonic nanostructures for thin-film silicon solar cells. We validate our method by relating the optical reflectance of the full solar cell stack to the external quantum efficiency of functional cells. Our method provides a useful experimental tool to compare different nanostructures circumventing complications arising from parasitic absorption and electrical cell performance.

We propose the use of transparent replicated random nanostructures fabricated via nanoimprinting on glass as next-generation superstrates for thin film silicon solar cells. We validate our approach by demonstrating short-circuit current densities for p-i-n hydrogenated microcrystalline silicon solar cells as high as for state-of-the-art nanotextured ZnO front electrodes. Our methodology opens exciting possibilities to integrate a large variety of nanostructures into p-i-n solar cells and allows to systematically investigate the influence of interface morphology on the optical and electronic properties of the device in order to further improve device performance.

Substrates with extremely low roughness to allow the growth of good-quality silicon material but that nevertheless present high light trapping properties are presented. In a first application, silver reflectors are used in single and tandem-junction amorphous silicon (a-Si:H) solar cells. High initial (stable) efficiencies of 10.4 % (8.1 %) for single-junction a-Si:H cells on glass and 11.1 % (9.2 %) for tandem-junction a-Si:H/a-Si:H cells on plastic are obtained. A second application better suited to multi-junction solar cells based on microcrystalline silicon (μc-Si:H) solar cells is presented: the substrate consists of rough zinc oxide (ZnO) grown on a flat silver reflector which is covered with a-Si:H; polishing of this structure yields an a-Si:H/ZnO interface that provides high light scattering even though the cell is deposited on a flat interface. We present results of ∼ 4-μm-thick μc-Si:H solar cells prepared on such substrates with high open-circuit voltages of 520 mV. A large relative efficiency gain of 20% is observed compared to a co-deposited cell grown directly on an optimized textured substrate.

In this paper, we investigate tandem amorphous/microcrystalline silicon solar cells with asymmetric intermediate reflectors grown in the n–i–p substrate configuration. We compare different types of substrates with respect to their light-trapping properties as well as their influence on the growth of single-junction microcrystalline cells. Our most promising back reflector combines a textured zinc oxide film grown by low-pressure chemical vapor deposition, a silver film for reflection, and a zinc oxide buffer layer. Grown on this substrate, microcrystalline cells exhibit excellent response in the infrared while keeping high open-circuit voltage and fill factor, leading to efficiencies of up to 10.0%. After optimizing the morphology of the asymmetric intermediate reflector, we achieve an n–i–p micromorph solar cell stabilized efficiency of 11.6%, using 270 nm and 1.7 mm of silicon for the absorber layer of the amorphous top cell and the microcrystalline bottom cell, respectively. Using this original device architecture, we reach efficiencies close to those of state-of-the-art n–i–p and p–i–n micromorph devices, demonstrating a promising route to deposit high-efficiency thin-film silicon solar cells on opaque substrates.

We investigate the transfer of random nanostructures commonly used in thin film silicon solar cells onto inexpensive substrates such as glass or flexible polyethylene sheets. Morphological and optical analyses of masters and replicas show the successful transfer of details with sizes much below 1 µm. These high quality replicas are obtained by UV nano imprinting avoiding the use of PDMS as an intermediate mold which has been identified as being responsible for the lack of resolution found in previous works. © 2010 Elsevier B.V. All rights reserved.

Thin film silicon solar cells are attractive for photovoltaics; however, the poor charge transport in this material requires that the devices are thinner than the absorption length. Adequate absorption can nevertheless be achieved by light scattering at textured interfaces because light can get trapped inside the absorber layer if it is scattered into angles above the critical angle of total internal reflection. This situation can be identified with the propagation of a guided mode in a waveguide where silicon plays the role of the high index guiding medium and the interface texture serves to couple the incident light to modes via grating coupling. We present an experimental realization of a solar cell structure on a line grating where the enhanced photocurrent can be clearly related to resonant excitation of waveguide modes.

Purpose: To establish predictive models for late objective aspiration and late patient-reported choking based on dose-volume parameters and baseline patient and treatment characteristics, for patients with head and neck cancer undergoing definitive radiotherapy (RT). The impact of electively treated volume on late aspiration was also investigated. Methods and material: This prospective cohort is a subsample of 124 survivors from the ARTSCAN study. Late aspiration was identified with videofluoroscopy, at a minimum of 25 months after the start of RT. Patient-reported choking was analysed at 12 and 60 months post RT using the EORTC Quality of Life Module for Head and Neck Cancer 35. Univariable and multivariable analyses were performed to describe the association between clinical factors and dose-volume descriptors for organs at risk (OARs) and late dysphagia. Results: Aspiration was found in 47% of the eligible patients. Mean dose to the middle pharyngeal constrictor (MPC), neck dissection post RT and age at randomisation in ARTSCAN were associated to late aspiration. Mean dose to the superior pharyngeal constrictor (SPC) and swallowing complaints at baseline were associated to patient reported choking at both time-points. Conclusions: Three separate risk groups for late aspiration, and two risk groups for late patient-reported choking were identified based on number of risk factors. The size of the electively treated volume could be used as a surrogate for individual OARs predicting late aspiration.

We investigate the influence of patterned metallic back reflector on absorption in thin-film silicon photovoltaics. The impact of symmetry, periodicity, and angle of incidence of light is discussed by simulation and experiment.