Search

This article presents for the first time the application of wet-chemical interfacial oxide from an industrial inline processing system for poly-Si-based passivating contacts. An excellent passivation quality is achieved by creating an interfacial oxide with a very short exposure time of 90 s in ozonized water and by adjusting the annealing temperature in a tube furnace, resulting in surface recombination current densities of 4 fA/cm2 and 1.2 fA/cm2 before and after a hydrogenation step, respectively. Detailed electrical characterization reveals the interplay of in-diffusion of P into the wafer and hydrogenation step. Our investigation shows that the optimum annealing temperature can differ before and after the hydrogenation step. The developed wet-chemical interfacial oxide is successfully implemented in back junction solar cells on large-area gallium-doped p-type silicon wafers (156.75 × 156.75 mm2) featuring a phosphorus-doped poly-Si-based passivating contact at the rear side. The best cell has an efficiency of 23.6% and an open-circuit voltage of 719 mV, independently confirmed by ISFH CalTeC in Germany. Our cost calculation shows a saving of up to 17.2% in capital expenditure, 5.2% p.a. in operating expense, and 9.0% in the footprint if the interfacial oxide is formed by an inline wet-chemical processing system instead of a plasma chamber.

Context: Plantar fasciitis (PF) is a common condition in active individuals. The lack of agreement on PF etiology makes treatment challenging and highlights the importance of understanding risk factors for preventive efforts.Objective: The purpose of this systematic review and meta-analysis was to determine what factors may put physically active individuals at risk of developing PF.Data Sources: CENTRAL, CINAHL, EMBASE, Gray Lit, LILACS, MEDLINE (PubMed), ProQuest, Scopus, SPORTDiscus, and Web of Science were searched through April 2018 and updated in April 2020.Study Selection: Studies were included if they were original research investigating PF risk factors, compared physically active individuals with and without PF, were written in English, and were accessible as full-length, peer-reviewed articles.Study Design: Systematic review and meta-analysis.Level of Evidence: Level 3, because of inconsistent definitions and blinding used in the included observational studies.Data Extraction: Data on sample characteristics, study design and duration, groups, PF diagnosis, and risk factors were extracted. The methodological quality of the studies was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology statement. When means and standard deviations of a particular risk factor were presented 2 or more times, that risk factor was included in the meta-analysis.Results: Sixteen studies were included in the systematic review and 11 risk factors in the meta-analysis. Increased plantarflexion range of motion (weighted mean difference [MD] = 7.04°; 95% CI, 5.88-8.19; P< 0.001), body mass index (MD = 2.13 kg/m2; 95% CI, 1.40-2.86; P< 0.001; I2= 0.00%), and body mass (MD = 4.52 kg; 95% CI, 0.55-8.49; P= 0.026) were risk factors for PF.Conclusion: Interventions focused on addressing a greater degree of plantarflexion range of motion, body mass index, and body mass and their load on the force-absorbing plantar surface structures may be a good starting point in the prevention and treatment of active individuals with PF.

Strings constructed from three-terminal tandem (3TT) solar cells offer the performance benefits of voltage-matching (which reduces sensitivity to spectral variation), but without the subcell voltage isolation required by four-terminal cells. However, the circuitry for a 3TT string can become complex, making circuit analysis more challenging. Here, we illustrate the essential features of “homogenous” voltage-matched (VM) 3TT strings, for which all 3TT cells in the string are nominally identical (with the same design/doping sequence, such that they can be fabricated on the same manufacturing line). Several representative VM string configurations are explicitly considered, and used to describe the general construction of string I(V) curves. End losses intrinsic to these strings are discussed in detail, along with mitigation strategies to minimize their impact. Our analysis agrees with experimental results for eight-cell strings constructed from GaInP/GaAs 3TT devices.

In this work, we demonstrate that partial shading of one solar cell in a state-of-the-art monocrystalline photovoltaic module with three bypass diodes results in hot cells with critical peak temperatures of 164 $^\circ$C. We examine two solar modules in the IEC 61215-2 MQT 09 hot-spot endurance test, one with 367.3 W$_\text{P}$ featuring 72 full-cells and the other with 388.6 W$_\text{P}$ featuring 144 half-cells. For the solar module with 72 solar cells, we measure a maximum temperature of 164 $^\circ$C, which results in a degradation of the encapsulation material and increases the risk of solar module failure. The high temperature results from the hot cell effect due to the power dissipation in the reverse-biased solar cell caused by partial shading. Our experiments show that the half-cell solar module is advantageous in terms of solar cell shading compared to the full-cell solar module. Although the half-cell solar module has a higher power output than the full-cell solar module, we measure a cooler peak temperature of 150 $^\circ$C. However, under certain shading conditions, the half-cell solar module can exhibit similar temperatures as the full-cell solar module. Based on our experimental results, we develop an electrical and a thermal model to predict the temperature of novel high-power solar modules with solar cells from larger silicon wafer formats in case of partial cell shading. Our predictions consider the trends of further increasing solar cell and module efficiencies, larger silicon wafer formats, and larger solar modules. We simulate a maximum peak temperature of 176 $^\circ$C at the solar module's surface, which significantly increases the risk of solar module failure. Our results show that new high-power solar modules employing solar cells that are made from larger silicon wafer formats need a new protection against overheating. Three bypass diodes per solar module are no longer sufficient.

Purpose:To examine relationships between sex, core stability endurance (CSE), and movement capacity in healthy, active adults.Methods:Fifty-three adults performed the functional movement screen (FMS) and CSE tests (extension, flexion, and right/left side bridge) during the current study. A generalized linear mixed model with random effects was used to identify interactions between sex, CSE, and FMS composite scores.Results:There was a significant triple interaction between CSE test, CSE score, and sex (There was a significant triple interaction between CSE test, CSE score, and sex (P< .001), indicating the relationship between CSE test scores and FMS differed by CSE test and sex. Analyses of each CSE test found significant interactions between sex and FMS scores for the CSE extension and right side bridge tests. CSE extension and right side bridge accounted for 43% and 40% of the variance in FMS composite scores in women, compared to 9% and less than 1% in men, respectively.Conclusions:CSE appears to contribute more to the movement capacity of women than men.[[Athletic Training & Sports Health Care. 2020;12(3):111–118.]

III–V/Si tandem solar cells have demonstrated efficiencies exceeding the theoretical efficiency limit of silicon solar cells. On the cell level, device modeling shows that three-terminal tandem (3T) devices with rear contacted bottom Si cells perform as well as operating the subcells independently (4T). However, integrating these 3T devices in a module requires voltage matching of the top and the bottom cell. Here, we investigate the robustness of parallel/series-interconnected 3T III–V/Si tandem devices in comparison with series-interconnected two terminal (2T) and independently operated (4T) devices with respect to spectral, thermal, and resistive effects. Under most conditions, interconnected 3T devices are able to perform as well as those with independent operation of the top and bottom cell, and 3T devices significantly outperform 2T devices.

We present a model for a yield analysis of tandem devices consisting of Si bottom cells with III-V top cells. It accounts for the spectral properties of the subcells as well as their reduced operating temperature due to increased efficiency and luminescent coupling. Inputs are the experimental I–V and QE data of the subcells (e.g., available from laboratory prototypes) and the irradiance-dependent module temperature of the bottom cell. We apply the model to compare two types of tandem cells, GaInP and GaAs top cells on Si bottom cells. The impact of the temperature model, compared to a constant temperature, shows a relative change in energy yield of up to 2.7%rel. Including luminescent coupling for GaAs/Si devices with two terminals, increases the energy yield by 34.0%rel. This is still 34.2%rel less energy yielded than for GaInP/Si two-terminal devices. The performance of the GaInP/Si devices can be improved by 5.8%rel using three-terminal devices with back-contacted bottom cells instead of a two-terminal configuration under the assumption of a cell string with voltage matching of one top cell with two bottom cells. For GaInP/Si, the three-terminal device performs similarly to the four-terminal device, enabling the integration of monolithic tandem cells into modules at comparably high efficiencies.

Purpose:To determine which provocative tests athletic trainers use during the evaluation of knee sprain injuries.Methods:A retrospective study of 263 athletic trainer evaluations of knee sprains (anterior/posterior cruciate ligaments = 103, medial collateral ligament = 120, lateral collateral ligament = 40) was conducted.Results:Athletic trainers reported using the Lachman (93.2%, n = 96), valgus stress (76.7%, n = 79), and anterior drawer (73.8%, n = 73.8) tests when assessing anterior/posterior cruciate ligament injuries. For the assessment of medial collateral ligament injuries, athletic trainers reported using the valgus stress (97.5%, n = 117), Lachman (80.0%, n = 96), and varus stress (73.3%, n = 88) tests most frequently. For the assessment of lateral collateral ligament injuries, the varus stress (85.0%, n = 34), valgus stress (85.0%, n = 34), and anterior drawer (72.5%, n = 29) tests were reported.Conclusions:The most frequently reported provocative tests for knee sprains were the Lachman, valgus and varus stress, and anterior and posterior drawer tests, regardless of the specific diagnosis.[[Athletic Training & Sports Health Care. 2018;10(2):69–75.]

Context: Increased pitch volume and altered glenohumeral (GH) and hip range of motion (ROM) and strength contribute to injury risk in baseball pitchers. Although these factors affect one another, whether they are related is unknown.Objective: To examine relationships among cumulative and seasonal pitch volume, ROM, and strength of the GH and hip joints in youth baseball pitchers.Design: Cross-sectional study.Setting: Baseball practice facilities.Patients or Other Participants: A total of 28 healthy baseball pitchers (age 13.9 ± 2.9 years).Main Outcome Measure(s): A demographic and pitching questionnaire was used to quantify pitch volume. Glenohumeral internal-rotation (IR) and external-rotation (ER) ROM and strength of the throwing arm; total arc of motion (IR ER ROM); and bilateral hip IR, ER, and total arc of motion ROM and strength in IR, ER, and abduction were measured. A goniometer was used to assess ROM; a handheld dynamometer, to assess strength. Frequency analyses and bivariate correlations (age covariate) described data and identified relationships.Results: Correlations between years of competitive play and increased strength in lead-leg hip IR (r 0.52, P .02) and abduction (r 0.48, P .04) and stance-leg hip IR (r 0.45, P .05) were fair to good. The number of months played in the last year had a fair correlation with decreased GH IR strength (r −0.39, P .04) and increased stance-leg hip IR strength (r 0.44, P .05). Limited pitch time had a fair correlation with increased GH ER ROM (r 0.40, P .04) and an excellent correlation with increased lead-leg hip IR ROM (r 0.79, P< .001). Increased innings pitched per game had a fair to good correlation with decreased GH IR strength (r −0.41, P .04) and stance-leg hip ER ROM (r −0.53, P .03). More pitches per game had a fair to good correlation with increased GH ER ROM (r 0.44, P .05) and decreased stance-leg hip ER ROM (r −0.62, P .008).Conclusions: The significant relationships identified in this study suggest the need to further examine youth and adolescent cumulative and seasonal pitch guidelines.

We examine the stability of the c-Si surface passivation quality by spatial atomic-layer-deposited aluminum oxide (Al2O3), plasma-enhanced chemical vapor deposited silicon nitride (SiNx), and Al2O3/SiNx stacks under illumination with two different spectra. The Al2O3-passivated c-Si surfaces annealed at 350 °C show a weak degradation due to UV illumination, with surface recombination velocities (SRVs) of 122 cm/s after receiving a ultraviolet (UV) dose of 275 kWh/m2. Silicon samples passivated with Al2O3 layers that received a fast-firing step show an improvement due to UV illumination with a reduction of the SRVs initially from 14 to 5 cm/s for single Al2O3 layers. For the fired Al2O3 layers the negative fixed charge density increases from -6×1012 cm-2 up to -1.2×1013 cm-2 during UV illumination. We demonstrate that for the SiNx and the fired Al2O3 single layers, photons with energy greater than 3.4 eV are necessary to reduce the passivation quality. In contrast, low-temperature-annealed Al2O3 single layers and nonfired Al2O3/SiNx stacks showed a degradation already under illumination with a halogen lamp. Importantly, we observe a perfectly stable passivation on boron-diffused p+ emitter for fired Al2O3/SiNx stacks featuring a stable saturation current density of 18 fA/cm2 for a p+ sheet resistance of 90 Ω/sq.

We process a photovoltaic (PV) module with 120 half passivated emitter and rear cells that exhibits an independently confirmed power of 303.2 W and a module efficiency of 20.2% (aperture area). The cells are optimized for operation within the module. We enhance light harvesting from the inactive spacing between the cells and the cell interconnect ribbons. Additionally, we reduce the inactive area to below 3% of the aperture module area. The impact of these measures is analyzed by ray-tracing simulations of the module. Using a numerical model, we analyze and predict the module performance based on the individual cell measurements and the optical simulations. We determine the power loss due to series interconnection of the solar cells to be 1.5%. This is compensated by a gain in current of 1.8% caused by the change of the optical environment of the cells in the module. We achieve a good agreement between simulations and experiments, both showing no cell-to-module power loss.

We demonstrate a reduced operating temperature of modules made from passivated emitter rear cells (PERCs) compared with modules made from cells featuring an unpassivated fullarea screen-printed aluminum rear side metallization aluminum back surface field (Al-BSF). Measurements on specific test modules fabricated from p-type silicon PERC and Al-BSF solar cells reveal a 4 °C lower operating temperature for the PERC module under 1400 W/m2 halogen illumination, if no temperature control is applied. For detailed analysis of the temperature effect, we perform a 3-D ray tracing analysis in the spectral range from 300 to 2500 nm to determine the radiative heat sources in a photovoltaic (PV) module. We combine these heat sources with a 1-D finite element method model solving the coupled system of semiconductor, thermal conduction, convection, and radiation equations for module temperature and power output. The simulations reveal that the origin of the reduced temperature of the PERC modules is a higher efficiency, as well as a higher reflectivity, of the cells rear side mirror. This reduces the parasitic absorptions in the rear metallization and increases the reflection for wavelengths above 1000 nm. This operating temperature difference is simulated to be linear in intensity. The slope depends on the spectral distribution of the incoming light. Under 1000 W/m2 in AM1.5G, our simulations reveal that the operating temperature difference is about 1.7 °C. The operating temperature can be lowered another 3.2 °C, if all parasitic absorption for wavelengths longer than 1200 nm can be prevented. Standard testing conditions applying a temperature control to the module do not show this effect of enhanced performance of the PERC modules. Yield calculations for systems in the field will thus systematically underestimate their electrical power output unless the inherently lower operating temperature of PERC modules is taken into account.

Context:The repetitive demands of throwing affect glenohumeral (GH) range of motion (ROM) and strength. Less is known about hip alterations in skeletally immature athletes.Objective:To compare GH and hip ROM and strength between age, position, and side of youth baseball athletes.Design:Cross-sectional study.Setting:Multicenter testing.Patients or Other Participants:Seventy-two healthy baseball athletes. Participants' self-reported characteristics were age group (7−11 years n 28 or 12−18 years n 44), position (pitcher n 22, position player n 47, unreported n 3), and side (throwing or nonthrowing arm, lead or stance leg).Main Outcome Measure(s):Bilateral GH and hip internal- and external-rotation ROM were measured passively and summed for total arc of motion (TAM). Glenohumeral and hip rotation and gluteus medius strength were measured. Analyses included linear mixed models.Results:Glenohumeral internal rotation was less in throwing than in nonthrowing arms (P< .05) except in younger pitchers (P .86). Compared with older athletes, younger athletes had more GH external rotation (103.3° ± 7.7° versus 97.5° ± 9.4°; P .002), TAM (156.4° ± 8.7° versus 147.9° ± 10.9°; P .04), and external rotation in throwing compared with nonthrowing arms (101.9° ± 1.2° versus 97.9° ± 1.1°; P< .001). Glenohumeral TAM was less in throwing than in nonthrowing arms (150.5° ± 2.1° versus 154.9° ± 1.3°; P .01). Younger athletes had more hip internal rotation (38.9° ± 6.8° versus 31.2° ± 7.5°; P< .001) and TAM (68.4° ± 10.0° versus 60.7° ± 9.8°; P .001) than older athletes. Lead-leg hip internal-rotation ROM was greater than in the stance leg (34.8° ± 8.9° versus 32.8° ± 7.7°; P .01). Overall, older players were stronger than younger players (P< .05), and the throwing arm was stronger in internal rotation than the nonthrowing arm (10.12 ± 3.72 lb 4.59 ± 1.69 kg versus 9.43 ± 3.18 lb 4.28 ± 1.44 kg; P .047).Conclusions:Youth baseball athletes had typical GH ROM adaptations of less internal rotation and more external rotation in the throwing versus the nonthrowing arm. Greater ROM in younger athletes may be explained by prepubertal characteristics. We obtained hip-strength values in youth baseball athletes, and as expected, older athletes were stronger.

Recent reports about new cell efficiency records are highlighting the continuing development of passivated emitter and rear cells (PERC). Additionally, volume production has started, forming the basis for cutting edge solar modules. However, transferring the high efficiency of the cells into a module requires an adaptation of the conventional front metallization and of the cell interconnection design. This paper studies and compares the module output of various cell interconnection technologies, including conventional cell interconnection ribbons and wires. We fabricate solar cells and characterize their electrical and optical properties. From the cells, we build experimental modules with various cell interconnection technologies. We determine the optical and electrical characteristics of the experimental modules. Based on our experimental results, we develop an analytical model that reproduces the power output of the experimental modules within the measurement uncertainty. The analytical model is then applied to simulate various cell interconnection technologies employing halved cells, optical enhanced cell interconnectors, and multiwires. We also consider the effect of enhancing the cell-to-cell spacing. Based on the experimentally verified simulations, we propose an optimized cell interconnection for a 60-PERC module that achieves a power output of 323 W. Our simulations reveal that wires combined with halved cells show the best module performance. However, applying light-harvesting structures to the cell interconnection ribbons is an attractive alternative for upgrading existing production lines.

Laser welding of thin Al layers offers a silver-free and highly flexible option for the interconnection of Al-metallized solar cells. Welding requires the melting of the Al layers in order to form a reliable electrical and mechanical contact. Here, we investigate the process driving the melt front of the aluminum, which is attached to a transparent substrate, toward the interface between the two Al layers. In experiments, we observe two different mechanisms depending on the thickness of the irradiated layer. In the case of Al layers thinner than 5 μm, a melt-through of the Al-layer is observed, whereas for thicker layers, thermal expansion causes a breakage of the surface and ejection of molten Al, which enables the contact formation. Using simulations that are based on the finite-element method, we instigate both mechanisms. The simulation results match the experimental observations within the measurement uncertainty. In case of thin layers, the simulation shows that the process is limited by thermal diffusion. For thicker Al layers, the onset of melting on the irradiated side initiates the breakage of the surface and the ejection of the aluminum.

Rehabilitation exercises to restore scapular stabilization promote balance in activation between the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) muscles. Research examining early stage scapular rehabilitation exercises is limited to asymptomatic adults. The study’s purpose was to determine whether scapular muscle activation ratios (UT/MT, UT/LT, and UT/SA) differ between glenohumeral joint pathology (n = 14) and asymptomatic controls (n = 12) during concentric and eccentric phases of five scapular stabilization rehabilitation exercises (2 per ratio). UT, MT, LT, and SA activity was measured using surface electromyography during concentric and eccentric phases of exercises. Activation ratios were calculated using normalized mean surface electromyography. Results found no group differences in activation ratio (Rehabilitation exercises to restore scapular stabilization promote balance in activation between the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) muscles. Research examining early stage scapular rehabilitation exercises is limited to asymptomatic adults. The study’s purpose was to determine whether scapular muscle activation ratios (UT/MT, UT/LT, and UT/SA) differ between glenohumeral joint pathology (n = 14) and asymptomatic controls (n = 12) during concentric and eccentric phases of five scapular stabilization rehabilitation exercises (2 per ratio). UT, MT, LT, and SA activity was measured using surface electromyography during concentric and eccentric phases of exercises. Activation ratios were calculated using normalized mean surface electromyography. Results found no group differences in activation ratio (P≥ .095), but did identify differences (P< .009) between concentric and eccentric phases of sidelying forward flexion, prone horizontal abduction/external rotation exercises. These findings can be a valuable resource for clinicians in developing a rehabilitation program that promotes desirable scapular muscle activation ratios. [Athletic Training & Sports Health Care.2015;7(4):151–159.]