Light Harvesting Schemes for High Efficiency Thin Film Silicon Solar Cells

In Thin Film Silicon (TF-Si) solar cells light harvesting schemes must guarantee an efficient light trapping in the thin absorber layers without decreasing the silicon layers quality and consecutively the p-i-n diodes electrical performance. TF-Si solar cells resilience to the substrate roughness is reported to be possibly improved through optimizations of the cell design and of the silicon deposition processes. By further tailoring the superstrate texture, amorphous silicon / microcrystalline silicon (a-Si:H/mu c-Si:H) tandem solar cells with an initial efficiency up to 13.7 % and a stabilized efficiency up to 11.8 % are demonstrated on single-scale textured superstrates. An alternative approach combining large and smooth features nanoimprinted onto a transparent lacquer with small and sharp textures from as-grown LPCVD ZnO is then shown to have a high potential for further increasing TF-Si devices efficiency. First results demonstrate up to 14.1 % initial efficiency for a TF-Si tandem solar cell

Effect of a lattice-matched GaAsSb capping layer on the structural properties of InAs/InGaAs/InP quantum dots

International audienceThe influence of a lattice-matched GaAsSb capping layer on the structural properties of self-assembled InAs quantum dots (QDs) grown on InP substrates is studied on the atomic scale by cross-sectional scanning tunneling microscopy. While lattice-matched In0.53Ga0.47As-capped QDs are clearly truncated pyramids, GaAs0.51Sb0.49-capped QDs grown under the same conditions look like full pyramids and exhibit a larger height, indicating that capping with GaAsSb reduces dot decomposition. Since there are no differences in strain between the two capping layers, this behavior is most likely related to the surfactant effect of Sb, which stabilizes the growth front and avoids adatom migration

Measurement of the Open-Circuit Voltage of Individual Subcells in a Dual-Junction Solar Cell

Dual-junction solar cells have the potential for higher conversion efficiencies than single junctions, thanks to a better utilization of the solar spectrum. However, their optimization is more complex because the monolithic interconnection makes the individual subcell electrical measurement difficult or impossible. This study presents a new technique to measure the open-circuit voltage VOC of each individual subcell of a dual-junction device with a method that circumvents the need for completely selective illumination. The method is based on the description of the total device VOC as a function of two independent variables determined by two distinct illumination spectra. Without completely selective illumination, one can measure only a limited range of this function; however, an unambiguous extension gives values corresponding to the conditions of ideal selectivity, which correspond in turn to the VOC of the individual subcells at 1-sun illumination. This method does not rely on any specific electrical or optical model of solar cell. Method is successfully tested with a simplemeasurement setup based on commercially available luminescence diodes and voltmeters in combination with specially prepared three-terminal dual-junction thin-film silicon solar cells

High-Stable-Efficiency Tandem Thin-Film Silicon Solar Cell With Low-Refractive-Index Silicon-Oxide Interlayer

We report the recent advances and key requirements for high-efficiency "micromorph" tandem thin-film silicon solar cells composed of an amorphous silicon top cell and a microcrystalline silicon bottom cell. The impact of inserting a low-refractive-index silicon-oxide (SiOx) film as intermediate reflecting layer (IRL) is highlighted. We show that refractive indexes as low as 1.75 can be obtained for layers still conducting enough to be implemented in solar cells, and without no additional degradation. This allows for high top-cell current densities with thin top cells, enabling low degradation rates. A micromorph cell with a certified efficiency of 12.63% (short-circuit current density of 12.8 mA/cm(2)) is obtained for an optimized stack. Furthermore, short-circuit current densities as high as 15.9 mA/cm(2) are reported in the amorphous silicon top-cell of micromorph devices by combining a 150-nm- thick SiOx-based IRL and a textured antireflecting coating at the air-glass interface

Study of InAs/InP(311)B stacked quantum dots for laser emission at 1.55 µm

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Amorphous silicon-germanium for triple and quadruple junction thin-film silicon based solar cells

We study amorphous silicon-germanium (a-SiGe:H) as intrinsic absorber material for thin-film silicon-based triple and quadruple junction solar cells. First, we present the development of a-SiGe:H single junction devices, in particular the Ge-content grading in the absorber layer, the influence of the Ge-content on electrical properties and (infra)red-response, and the influence of using different types of players. We subsequently show the incorporation of optimized single-junction devices in triple junction cells and discuss the interplay between Ge-content and intermediate reflector thickness. For triple junction devices with amorphous silicon (a-Si:H) top cells, a-SiGe:H middle cells and microcrystalline silicion (mu c-Si:H) bottom cells, we obtained an initial efficiency of 13.6% and an efficiency of 11.3% after light-soaking. We also present a quadruple junction device with an a-Si:H top cell, a low Ge-content a-SiGe:H second cell, and mu c-Si:H third and bottom cells. In this device configuration, we obtained an open-circuit voltage as high as 2.57 V. The performance of these cells was limited by not yet optimized current matching, leading nevertheless to an initial efficiency of 10.1%. A brief roadmap towards quadruple-junction devices with stabilized efficiencies of 14% is also outlined. (C) 2014 Elsevier B.V. All rights reserved

Light harvesting schemes for high efficiency thin film silicon solar cells

Objectives Patient recall of medical information is usually poor. Healthcare providers can employ affect-oriented (i.e., showing care) or cognition-oriented communication styles (i.e., structuring information) to enhance recall, but research evidence is limited especially among clinical and/or older patient populations. This video-vignette study manipulated provider caring and information structuring to examine effects on recall and trust among cancer patients/survivors. Methods In an online survey, 148 participants (Mage = 62) were randomized to one of four video conditions in a two (standard communication vs. enhanced caring) by two (standard vs. enhanced structuring) design, and completed measures of active recall, recognition, and trust. Results Increased caring or structuring did not enhance active recall or recognition, instead both were higher among younger, female, or highly educated participants. The caring condition induced higher perceived trust in the provider within the whole sample, but trust was significantly correlated with decreased recall (r = −.268) among younger participants. Conclusions Provider caring can strengthen the patient-provider relationship by enhancing trust. Yet, increased trust may impair recall among younger patients. Structuring treatment information did not enhance recall and recognition, but additional research is needed. Practice implications Providers may use additional ways of structuring/organizing information to help enhance recall (e.g., written information)

Association between prophylactic angiotensin-converting enzyme inhibitors and overall survival in Duchenne muscular dystrophy—analysis of registry data

International audienceAims: To estimate the effect of prophylactic angiotensin-converting enzyme inhibitors (ACEi) on survival in Duchenne muscular dystrophy (DMD).Methods and results: We analysed the data from the French multicentre DMD Heart Registry (ClinicalTrials.gov: NCT03443115). We estimated the association between the prophylactic prescription of ACEi and event-free survival in 668 patients aged 8 to 13 years, with normal left ventricular function, using (i) a Cox model with intervention as a time-dependent covariate, (ii) a propensity-based analysis comparing ACEi treatment vs. no treatment, and (iii) a set of sensitivity analyses. The study outcomes were overall survival and hospitalizations for heart failure (HF) or acute respiratory failure. Among the 668 patients included in the DMD Heart Registry, 576 (mean age 6.1 ± 2.8 years) were eligible for this study, of whom 390 were treated with ACEi prophylactically. Death occurred in 53 patients (13.5%) who were and 60 patients (32.3%) who were not treated prophylactically with ACEi, respectively. In a Cox model with intervention as a time-dependent variable, the hazard ratio (HR) associated with ACEi treatment was 0.49 [95% confidence interval (CI) 0.34-0.72] and 0.47 (95% CI 0.31-0.17) for overall mortality after adjustment for baseline variables. In the propensity-based analysis, 278 patients were included in the treatment group and 834 in the control group, with 18.5% and 30.4% 12-year estimated probability of death, respectively. ACEi were associated with a lower risk of death (HR 0.39; 95% CI 0.17-0.92) and hospitalization for HF (HR 0.16; 95% CI 0.04-0.62). All other sensitivity analyses yielded similar results.Conclusion: Prophylactic ACEi treatment in DMD was associated with a significantly higher overall survival and lower rates of hospitalization for HF