Effective Lifetime Research Articles

Radiation exposure and cancer risk of pediatric head CT scans: Impact of age and scanning parameters

Computed tomography (CT) is a widely utilized imaging technique in various medical applications due to the advanced technology that allows the diagnosis of diseases efficiently. The aims of this study were (1) to assess the radiation dose and the probability of cancer incidence for pediatric head CT scans, and (2) to analyze the influence of age and other scanning parameters on radiation dose. A total of 224 pediatric patients, ranging in age from newborn to 18 years, were collected from three main hospitals in Saudi Arabia. The patient data were divided into four age groups: Group 1 (0 to < 1 year old), Group 2 (1 to < 5 years old), Group 3 (5 to < 10 years old), and Group 4 (10 to < 18 years old). Initially, descriptive statistics were conducted for the values of volume CT dose index (CTDIvol), dose-length product (DLP), effective dose, and probability of lifetime cancer risk. This was followed by applying the Kruskal-Wallis H and the Mann-Whitney U tests to investigate the influence of age and other scanning parameters, namely tube voltage, slice thickness, and the use of automatic tube current modulation (ATCM), on radiation dose. It has been found that as the age of patients increased, there was a corresponding increase in CTDIvol and DLP values and a decrease in effective doses and lifetime cancer risk. The patient's age accounted for 33.4% and 34.9% of the variations in CTDIvol and DLP, respectively, while tube voltage (kVp) settings accounted for 25.8% and 24.9%, respectively. There was an increase of 22.3% in CTDIvol reported for patients scanned with a slice thickness of 2 mm compared to those scanned at 2.5 mm, and a 2.2% dose increase between slice thicknesses of 2.5 mm and 5 mm. Radiation doses in the surveyed hospitals fall within acceptable limits. Further studies in Saudi Arabia should focus on evaluating patient doses based on the actual sizes, which determine radiation doses for pediatric CT imaging more accurately.

Analysis of internal gamma-ray dose to the public from brick as building material in Tamil Nadu, India.

Natural radioactivity due to 238U, 232Th and 40K in brick samples from Tamil Nadu was determined using gamma-ray spectrometry. The mean activity concentrations of 238U, 232Th and 40K, 69±6, 62±6 and 462±23Bqkg-1, are slightly greater than the world recommended limits of 35, 45 and 420Bqkg-1, respectively, and they are compared with a similar work carried out across the world. The radiological parameters such as radium equivalent activity, Raeq (193±17Bqkg-1), internal hazard index, Hin (0.71±0.06), and activity utilisation index, AUI (1.43±0.13), was lower, whilst absorbed dose rate, DRin (89±8 nGy h-1), annual effective dose equivalent, AEDEin (0.43±0.04mSv y-1), and excess lifetime cancer risk, ELCRin (1.52±0.13mSv y-1), are slightly greater than the world's recommended limit. Bi-variate statistical analysis was performed to corroborate the relationship between radionuclides and radiological hazards.

Broadband-Spectral-Responsivity of black silicon photodetector with high gain and sub-bandgap sensitivity by titanium hyperdoping

Silicon, as one of the most essential semiconducting materials, is widely applied in various photodetection applications due to its high portability, convenient preparation, and compatibility with conventional complementary metal–oxide–semiconductor technology. Nowadays, black silicon, prepared by enforcing ultrafast laser micro-structuring and hyperdoping techniques, has received considerable attention for developing next-generation silicon photonics and silicon optoelectronics devices. In this work, high-comprehensive-property black silicon photodetectors with broadband spectral responsivity and high gain were achieved by femtosecond laser irradiation and titanium hyperdoping. The proposed device can respond to the incident light from 400 nm to at least 1550 nm, demonstrating a high responsivity of 40.59 A/W for 950 nm under the application of −5 V bias, and the corresponding detectivity can reach 3.61 × 1012 cm·Hz1/2W−1. Moreover, the fabricated photodetector exhibits a stable sub-bandgap photocurrent at 1550 nm, with an average responsivity of 3.42 mA/W by applying a −5 V bias. These improvements were achieved by the hyperdoping of titanium in silicon, which shows deep impurity levels, low electroactivity, and increased effective carrier lifetimes, as well as the formation of shallow n-i heterojunction and trapping centers induced by the femtosecond laser irradiation. Our work provides significant insights into the applications of black silicon in various optical-related fields, including weak and infrared photon detection, silicon photonic chips, remote sensing, and large-scale optoelectronic integration.

Evaluation of total effective dose and excess lifetime cancer risk associated with tin mining activities in Nigeria using generic and resrad simulation methods

Soil excavation in search of mineral ores serves as one of means of livelihood to many families in Nigeria. Even though the process was found to be associated with many concerns pertaining to radiological health, which many of the mining workers and dwellers around the sites are unaware of. In an effort to bridges this gap and provide a handful of information, the activity concentrations of 40K, 226Ra, and 232Th from typically well-known tin mining areas in Nigeria were evaluated using the higher purity germanium detector. The state-of-the-art software RESRAD-ONSITE and generic approaches were employed to evaluate the dose and cancer risk attributable to radiation exposure due to the measured radionuclides in soil. Depending on the thickness of contamination, the results obtained show dose and cancer risk value greater than the acceptable limit of 1 mSv/yr for members of the public as set by the Nigerian Nuclear Regulatory Authority, the United States Environmental Protection Agency, and the International Committee on Radiological Protection's cancer risk threshold of 4.3 × 10−3. Therefore, sustainable mining practices should be implemented across the tin mining areas in Nigeria to avert the perceived radiation related effects.

Persistent Charging of CsPbBr3 Perovskite Nanocrystals Confined in Glass Matrix.

Manipulation of persistent charges in semiconductor nanostructure is the key point to obtain quantum bits towards the application of quantum memory and information devices. However, realizing persistent charge storage in semiconductor nano-systems is still very challenge due to the disturbance from crystal defects and environment conditions. Herein, the two-photon persistent charging induced long-lasting afterglow and charged exciton formation are observed in CsPbBr3 perovskite nanocrystals (NCs) confined in glass host with effective lifetime surpassing one second, where the glass inclosure provides effective protection. A method combining the femtosecond and second time-resolved transient absorption spectroscopy is explored to determine the persistent charging possibility of perovskite NCs unambiguously. Meanwhile, with temperature-dependent spectroscopy, the underlying mechanism of this persistent charging is elucidated. A two-channel carrier transfer model is proposed involving athermal quantum tunneling and slower thermal-assisted channel. On this basis, two different information storage devices are demonstrated with the memory time exceeding two hours under low-temperature condition. These results provide a new strategy to realize persistent charging in perovskite NCs and deepen the understanding of the underlying carrier kinetics, which may pave an alternative way towards novel information memory and optical data storage applications.

A Review on Synthesis and Physicochemical Properties-Photocatalytic Activity Relationships of Carbon Quantum Dots Graphitic Carbon Nitride in Reduction of Carbon Dioxide

Carbon dioxide (CO2) is a major greenhouse gas present in over half of the Earth's atmosphere. Elevated CO2 emissions in the atmosphere have become a global warming issue due to the excessive use of fossil fuels by human activities. Converting CO2 into a useful compound is crucial since CO2 exists in the environment and must be reduced. The use of semiconductor materials in photocatalysis is the best solution to degrade and potentially convert CO2 into a useful energy source. Recently, research on graphitic carbon nitride (g-C3N4) has developed interest due to its phenomenal properties, such as effective charge separation and charge carrier lifetime, electron-hole recombination, and high surface area. CQDs/g-C3N4 has recently emerged as a novel technology due to its excellent physical and chemical properties, especially in the reduction of CO2. Thus, this review outlines the recent modification of graphitic carbon nitride (g-C3N4) by carbon quantum dots (CQDs), which include the synthesis of CQDs/g-C3N4 for CO2 reduction. Lastly, the review discusses physicochemical properties-photocatalytic activity relationship of CQDs/g-C3N4 in the photocatalytic reduction of CO2. This review provides a wide range of perspectives and a guideline for designing the more effective CQDs/ g-C3N4 for photocatalytic reduction of CO2.

Maskless fabrication of quasi-omnidirectional V-groove solar cells using an alkaline solution-based method

Silicon passivated emitter and rear contact (PERC) solar cells with V-groove texture were fabricated using maskless alkaline solution etching with in-house developed additive. Compared with the traditional pyramid texture, the V-groove texture possesses superior effective minority carrier lifetime, enhanced p–n junction quality and better applied filling factor (FF). In addition, a V-groove texture can greatly reduce the shading area and edge damage of front Ag electrodes when the V-groove direction is parallel to the gridline electrodes. Due to these factors, the V-groove solar cells have a higher efficiency (21.78%) than pyramid solar cells (21.62%). Interestingly, external quantum efficiency (EQE) and reflectance of the V-groove solar cells exhibit a slight decrease when the incident light angle (θ) is increased from 0° to 75°, which confirms the excellent quasi omnidirectionality of the V-groove solar cells. The proposed V-groove solar cell design shows a 2.84% relative enhancement of energy output over traditional pyramid solar cells.

Blistering-free carbon-doped polysilicon (n+) passivating contact with high surface passivation properties prepared by industrial tube PECVD

Tube plasma-enhanced chemical vapor deposition (PECVD) has garnered attention as a promising large-scale production tool for in-situ doped polysilicon due to its high capacity and low equipment cost. In this work, we explore the use of carbon (C)-doped a-Si:H (n+), deposited by tube PECVD, for tunnel oxide passivated contact (TOPCon) solar cells. By introducing carbon atoms into polysilicon, blistering-free polysilicon films with excellent passivation properties can be obtained. The optimized sample with C-doped polysilicon (n+) exhibits remarkable surface passivation with a single-sided saturation current density (J0,s) of 1.25 fA/cm2, an implied open-circuit voltage (iVoc) of 751 mV, and a corresponding effective lifetime exceeding 18 ms at a minority carrier concentration of 1 × 1015 cm−3. UV Raman measurements reveal that C doping suppresses the crystallization of polysilicon, leading to a significant stress in the film. Despite excessive C doping, the contact resistivity extracted from the TLM method remains below 13.6 mΩ cm2. As a result, a champion conversion efficiency of 23.64 % was achieved in a small-sized proof-of-concept n-type TOPCon solar cell. This demonstrates the feasibility of fabricating C-doped polysilicon (n+) prepared by tube PECVD for high-efficiency and low-cost TOPCon solar cells.

Analysis of the Effect of Radiation Defects by Low-energy Protons on Electrophysical Properties of Silicon N+ -P-P+Structure

Nowadays, radiation engineering is a promising direction in the creation of semiconductor devices. The proton irradiation is used to controllably change the optical, electrical, recombination, mechanical and structural properties of the semiconductors. Low-energy protons make it possible to purposefully change material properties near the surface where the n+ -p junction is located. In this paper, the impact of low-energy protons on the electro physical parameters of n+ -p-p+ silicon photoelectric converters (SPC) is analyzed. The current-voltage characteristics and switching time of these SPCs are measured. The switching time is determined using rectangular bipolar voltage pulses with an amplitude of 10 mV, a frequency of 200 kHz, or a frequency of 1 MHz. A theoretical and experimental analysis of the obtained results is performed. The comparison of experimental data with the results of calculations shows that protons with an energy of 180 keV and a dose of 1015 cm–2 create two regions in the space charge region of the n+ -p junction with different switching times of 4.2 × 10–7 s and 5.5 × 10–8 s. SPC frequency characteristics have been improved by reducing the effective lifetime by 5-10 times. This effect can be used to create high-speed photodiodes with an operating modulation frequency of 18 MHz.

Excellent crystalline silicon surface passivation by transparent conductive Al-doped ZnO/ITO stack

The surface passivation materials commonly used in crystalline silicon (c-Si) solar cells are either electrically insulating or opaque to the solar spectrum, which poses the electrical loss or optical loss. Hence it is of great significance to explore functional films that are simultaneously transparent, conductive and passivating for c-Si. In this study, we successfully tune two most well-known transparent conductive oxides, i.e. Al-doped ZnO (AZO) and indium tin oxide (ITO), as excellent passivation layers for c-Si surface. The AZO film is grown by atomic layer deposition and is capped with a magnetron-sputtered ITO film. Dynamic secondary ion mass spectrometry reveals that such stack design can retain higher hydrogen concentration on c-Si surface than a single AZO film during annealing. In addition, the AZO should be highly doped to reduce the energy barrier height around c-Si surface, thereby increasing the charge carrier asymmetry and thus reducing surface recombination. It is also highly crucial to optimize the annealing temperature and interfacial silicon oxide. As such, the effective minority carrier lifetime reaches 2.0 ms and the implied open-circuit voltage approaches 700 mV. Besides, the AZO/ITO stacked films possess negligible optical absorption, low sheet resistance (∼90 Ω/sq), and outstanding antireflection effect on c-Si surface.

Ingestion exposure of public to natural radionuclides and committed effective dose and cancer risk through tuber crops cultivated in Ebonyi State, Nigeria.

Internal exposure of public to radiation arising from ingestion of natural radionuclides in tuber crops of Ebonyi State origin was investigated in this study. Committed effective doses and lifetime cancer risk of 40K, 226Ra, and 232Th in cassava, cocoyam, water yam, and white yam were calculated. The average activity concentrations of 40K, 226Ra, and 232Th determined by gamma spectrometric Na (TI) detector were, respectively, 199.15 ± 23.51, 77.57 ± 7.98, and 118.20 ± 10.72 Bq/kg in cassava; 146.62 ± 40.69, 43.42 ± 7.63, and 75.61 ± 2.89 Bq/kg in cocoyam; 162.81 ± 20.43, 63.17 ± 11.36, and 81.50 ± 10.27 Bq/kg in water yam; and 184.50 ± 20.22, 80.23 ± 10.93, and 116.29 ± 5.93 Bq/kg in white yam. The total committed effective dose via ingestion aligned in this orderof cassava (7.05 mSv/year) > white yam (4.38 mSv/year) > water yam (0.42 mSv/year) > cocoyam (0.21 mSv/year) with overall average dose of 3.12 mSv/year. The values of dose were higher than world average of 0.29 mSv/year given by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The lifetime cancer risk values were above tolerance level of >10-4 prescribed by United States Environmental Protection Agency (USEPA), suggesting probable evolvement of radiogenic cancer morbidity. The data presented in this study contributes to baseline information on radiological characteristics of tuber crops in Ebonyi, which would be valuable to WHO/FAO food safety policy in Nigeria and rest of the world.

Adequate method to study the surface passivation effectiveness in HEM multicristallin silicon wafers

In this work we have examined the effectiveness of surface passivation on ascut multicrystalline silicon (mc-Si) wafers using different techniques. The study is based on minority carrier lifetime measurements with quasi steady state photo-conductance, ‘QSSPC’. Effective minority carrier lifetime ()measured values of 12.4, 8.9, 4.9 and 3.1 are obtained respectively with four silicon surface passivation techniques: 1- Shallow phosphorous diffusion emitter (n+p), 2- Iodine-Ethanol (I-E), 3-Hydrofluoric acid (HF) emersion and 4-SiNx layer deposition. These results suggest that the shallow n+p emitter gives the eff close to the bulk lifetime due to the better surface passivation quality. Simulations made with Hornbeck-Haynes model indicate that the improvement can be correlated with the decrease of the surface recombination velocity (SRV) and the increment of bulk lifetime.

Optical modeling and characterization of bifacial SiNx/AlOx dielectric layers for surface passivation and antireflection in PERC

AbstractIn this research, we analyzed the impact that the optical characteristics of dielectric surface passivation and antireflection coating schemes have on the performance of passivated emitter and rear cell (PERC) silicon solar cells. We employed wafer ray tracer (WRT) and automate for simulation of heterostructure (AFORS‐HET) simulations, as well as experimental characterization of fabricated thin film coatings. We investigated three distinct front surface morphologies: planar surface, upright pyramids, and inverted pyramids. Using WRT, we calculated the photogeneration current densities (JG) for PERC devices with three schemes: (i) SiNx/AlOx as antireflection coating and passivation stacks on both the front and rear sides, (ii) SiNx antireflection coating on the front side and AlOx passivation layer on the rear side, and (iii) SiNx/AlOx as antireflection coating and passivation stacks on the front side with an AlOx passivation layer on the rear side. Following simulation with optimal JG, two schemes are experimentally evaluated: PECVD SiNx (70 nm) and atomic layer deposition (ALD) AlOx (15 and 25 nm). We confirmed the growth effects and optical properties using X‐ray diffraction, Raman spectroscopy, effective lifetime, and refractive index measurements. The most favorable electrical properties were obtained with SiNx (70 nm, front) and AlOx (25 nm, front and rear), where the AlOx can be deposited via ALD bifacially on a single step, minimizing processing while maintaining passivation performance. Finally, we used AFORS‐HET to simulate the maximum performance of PERC bearing such films. The results showed a Voc = 0.688 V, Jsc = 41.42 mA/cm2, FF = 84%, and packing conversion efficiency (PCE) = 24.12% as the optimal solar cell performance values.

Development of Theoretical Model for Effective Carrier Lifetime in Polycrystalline Semiconductors

Development of Theoretical Model for Effective Carrier Lifetime in Polycrystalline Semiconductors

Measurement of the Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document}→ μμ effective lifetime with the ATLAS detector

This paper reports the first ATLAS measurement of the Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document}→ μμ effective lifetime. The measurement is based on the data collected in 2015–2016, amounting to 26.3 fb−1 of 13 TeV LHC proton-proton collisions. The proper decay-time distribution of 58 ± 13 background-subtracted signal candidates is fit with simulated signal templates parameterised as a function of the Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document} effective lifetime, with statistical uncertainties extracted through a Neyman construction. The resulting effective measurement of the Bs0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {B}_s^0 $$\\end{document}→ μμ lifetime is 0.99−0.07+0.42\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {0.99}_{-0.07}^{+0.42} $$\\end{document} (stat.) ± 0.17 (syst.) ps and it is found to be consistent with the Standard Model.

Longitudinal-optical-phonon resonant thermal emission efficiency and spectrum control of metal-GaAs surface micro-stripe structures

Phonon-based tera-Hertz or mid-infrared emission has been investigated because it can be applied to high-efficiency light sources for optical communication and material diagnostics, where thermal energy can be utilized as an energy source of emission. Particularly, nano- and micro-surface structures have been investigated for versatile emission controllability. We present the polarized longitudinal optical (LO) phonon resonant thermal emission of radiation (LORE) peaked at approximately 8.5 THz in a range of 450–650 K from simple surface Au–GaAs–Au micro-stripe structures on undoped (u-) GaAs wafers, where the metal component, which has been avoided for surface phonon polariton (SPhP) emission, is introduced. This LORE is based on electric dipoles formed by coherently oscillating polarization charges on pairs of interfaces and has a feature of structure size or emission direction-independent frequency, which is quite different from the properties of SPhPs. The dependence of emission properties on structural factors and temperature reveals the approximately evenly matched radiative and nonradiative LO-phonon annihilation rates in the local surface field and shows the controllability of emission and absorption balance based on the surface structures. Higher emission efficiency in the higher temperature region is found for structures with narrow emission windows of less than 2 μm. The decrease in the volume occupied by electric dipoles reduces the reabsorption probability of LORE, which shortens the effective radiative lifetime and, resultantly, increases the fraction of the radiative rate in the total annihilation rate. By comparing the emission from a pure graphite wafer, a short LORE mean time interval of approximately 2 ps is found. The background emission subject to Planck’s law is significantly reduced particularly in the region of 250–300 cm−1 using emission window widths narrower than 2 μm because of the sub-diffraction phenomenon.

The Impact of the Micro-Structure within Passivated Layers on the Performance of the a-Si:H/c-Si Heterojunction Solar Cells

This study investigated the correlation between the degree of disorder of the post-hydrogen plasma treatment (HPT) of the intrinsic hydrogenated amorphous silicon (a-Si:H(i)) and the device characteristics of the a-Si:H/c-Si heterojunction (HJ) solar cells. The reduction in the degree of disorder helps to improve interface defects and to enhance the effective carrier lifetime of the a-Si:H/c-Si heterojunction. The highest effective minority carrier lifetime of 2.08 ms was observed in the film with the lowest degree of disorder of 2.03. The devices constructed with HPT a-Si:H(i) having a lower degree of disorder demonstrated higher device performance in terms of open-circuit voltage (Voc), fill factor (FF), and subsequent conversion efficiency. An a-Si:H(i) with a lower degree of disorder (2.03) resulted in a higher Voc of 728 mV and FF of 72.33% and achieved a conversion efficiency of up to 20.84% for the a-Si:H/c-Si HJ silicon solar cell.

Influence of focusing intensity on optically pumped metastable rare gas based on laser-induced ionization

When traditional optically pumped metastable rare gas laser (OPRGL) operating in high power output, a potential issue may arise: electromagnetic interference (EMI) caused by large volume atmospheric pressure discharge. This EMI problem imposes limitations on the application of OPRGL. We propose a new idea of preparing metastable atoms by 532 nm laser-induced preionization, which has the potential to circumvent the EMI problem. An 811.5 nm laser was used to excite the metastable (4s[3/2]2) Ar atoms in Ar-He mixture, resulting in the generation of a prominent amplified spontaneous emission (ASE) signal at 912.3 nm (4p[1/2]1→4s[3/2]2). By investigating intensities of the 912.3 nm fluorescence and ASE as a function of the delay time between 811.5 nm and 532 nm lasers, the influence of the 532 nm laser's focusing intensity on the evolution of prepared metastable atomic concentration was unveiled, as well as the amplification mechanism of 912.3 nm signal. Furthermore, the competition mechanism between ASE and the fluorescence channels originating from the 4p[1/2]1 level was studied. Considering the influence of plasma expansion on metastable atomic concentration, as well as the influences of threshold, gain and gain length on ASE, at the “photoexcitation + radiation + collisional relaxation” stage, we obtained a reliable effective lifetime of the metastable 4s[3/2]2 level through analysis of the decay curve of the 912.3 nm ASE intensity. Similarly, in the “ion-electron recombination” stage, a reliable effective lifetime of the metastable 4s[3/2]2 level was obtained by analyzing the decay curve of the 912.3 nm fluorescence intensity. Additionally, the 912.3 nm ASE pulse width was influenced by various factors, including the effective lifetime of the 4p[1/2]1 level, the concentration of metastable Ar, the plasma expansion rate, and the gain length, etc. This work demonstrates that OPRGL based on laser-induced preionization offers a promising alternative for the future advancement of OPRGL.

Exploring the Potential of Pure Germanium Kesterite for a 2T Kesterite/Silicon Tandem Solar Cell: A Simulation Study.

Recently, the development of tandem devices has become one of the main strategies for further improving the efficiency of photovoltaic modules. In this regard, combining well-established Si technology with thin film technology is one of the most promising approaches. However, this imposes several limitations on such thin film technology, such as low prices, the absence of scarce or toxic elements, the possibility to tune optical properties and long lifetime stability. Therefore, to show the potential of kesterite/silicon tandems, in this work, a 2 terminal (2T) structure using pure germanium kesterite was simulated with combined SCAPS and transfer matrix methods. To explore the impact of individual modifications, a stepwise approach was adopted to improve the kesterite. For the bottom sub cell, a state-of-the-art silicon PERC cell was used with an efficiency of 24%. As a final result, 19.56% efficiency was obtained for the standalone top kesterite solar cell and 28.6% for the tandem device, exceeding standalone silicon efficiency by 4.6% and justifying a new method for improvement. The improvement observed could be attributed primarily to the enhanced effective lifetime, optimized base doping, and mitigated recombination at both the back and top layers of the CZGSSe absorber. Finally, colorimetric analysis showed that color purity for such tandem structure was low, and hues were limited to the predominant colors, which were reddish, yellowish, and purple in an anti-reflective coating (ARC) thickness range of 20-300 nm. The sensitivity of color variation for the whole ARC thickness range to electrical parameters was minimal: efficiency was obtained ranging from 28.05% to 28.63%.

Impact of Inbreeding and Ancestral Inbreeding on Longevity Traits in German Brown Cows.

A recent study on the population structure of the German Brown population found increasing levels of classical and ancestral inbreeding coefficients. Thus, the aim of this study was to determine the effects of inbreeding depression and purging on longevity traits using classical and ancestral inbreeding coefficients according to Kalinowski (2002) (Fa_Kal, FNew), Ballou (1997) (Fa_Bal), and Baumung (2015) (Ahc). For this purpose, uncensored data of 480,440 cows born between 1990 and 2001 were available. We analyzed 17 longevity traits, including herd life, length of productive life, number of calvings, lifetime and effective lifetime production for milk, fat, and protein yield, the survival to the 2nd, 4th, 6th, 8th, and 10th lactation number, and the culling frequencies due to infertility, or udder and foot and leg problems. Inbreeding depression was significant and negative for all traits but for culling due to udder and to foot and leg problems. When expressed in percentages of genetic standard deviations, inbreeding depression per 1% increase in inbreeding was -3.61 to -10.98%, -2.42 to -2.99%, -2.21 to -4.58%, and 5.13% for lifetime production traits, lifetime traits, survival rates, and culling due to infertility, respectively. Heterosis and recombination effects due to US Brown Swiss genes were positive and counteracted inbreeding depression. The effects of FNew were not significantly different from zero, while Fa_Kal had negative effects on lifetime and lifetime production traits. Similarly, the interaction of F with Fa_Bal was significantly negative. Thus, purging effects could not be shown for longevity traits in German Brown. A possible explanation may be seen in the breed history of the German Brown, that through the introgression of US Brown Swiss bulls ancestral inbreeding increased and longevity decreased. Our results show, that reducing a further increase in inbreeding in mating plans is advisable to prevent a further decline in longevity due to inbreeding depression, as purging effects were very unlikely in this population.