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Elucidating the mechanism of potential induced degradation delay effect by ultraviolet light irradiation for p-type crystalline silicon solar cells
摘要： A mechanism of potential induced degradation (PID) delay effect by ultraviolet (UV) light irradiation during PID test for p-type crystalline silicon (c-Si) solar cells was proposed in this work. The degradation rate of the solar cell performances is slowed down by the UV light irradiation in the 300–390 nm wavelength range during PID test. The conductivity increase of the silicon nitride (SiNx) anti-reflection coating (ARC) layer on the solar cell surface under UV light irradiation during PID tests, which relates to the mechanism preventing the penetration of sodium ions into the active cell layer, induces the PID delay effect for the p-type c-Si solar cells. The PID delay effect was also analyzed by a microwave photo-conductance decay (μ-PCD) technique in this work. The reduction behavior of the components in the μ-PCD signal curves including rapid (τ1) and slow (τ2) decay time constants and the effective lifetime (τeff) presents a good correlation with the performance degradation behavior of the solar cells over PID test duration. Moreover, the reduction rate of these components is also slowed down under the UV light irradiation in the 300–390 nm wavelength range during PID tests. Notably, their reduction behavior was compatible with the mechanism of the conductivity increase of the SiNx ARC layer under UV light irradiation.
关键词： Potential induced degradation (PID),Silicon solar cells,UV irradiation,Silicon nitride (SiNx),Microwave photo-conductance decay
更新于2025-09-23 15:19:57
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On the Question of the Need for a Built-In Potential in Perovskite Solar Cells
摘要： Perovskite semiconductors as the active materials in efficient solar cells exhibit free carrier diffusion lengths on the order of microns at low illumination fluxes and many hundreds of nanometers under 1 sun conditions. These lengthscales are significantly larger than typical junction thicknesses, and thus the carrier transport and charge collection should be expected to be diffusion controlled. A consensus along these lines is emerging in the field. However, the question as to whether the built-in potential plays any role is still of matter of some conjecture. This important question using phase-sensitive photocurrent measurements and theoretical device simulations based upon the drift-diffusion framework is addressed. In particular, the role of the built-in electric field and charge-selective transport layers in state-of-the-art p–i–n perovskite solar cells comparing experimental findings and simulation predictions is probed. It is found that while charge collection in the junction does not require a drift field per se, a built-in potential is still needed to avoid the formation of reverse electric fields inside the active layer, and to ensure efficient extraction through the charge transport layers.
关键词： perovskite solar cells,charge collection,built-in potential,charge transport layers
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-TW) - YILAN, Taiwan (2019.5.20-2019.5.22)] 2019 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-TW) - Lightweight Image De-raining for IoT-enabled Cameras
摘要： Statistical approaches for quantitative precipitation nowcasts (QPNs) have emerged with recent advances in sensors in geostationary orbits, which provide more frequent observations at higher spatial resolutions. Advanced Meteorological Imager (AMI) onboard South Korea’s second geostationary satellite (GEO-KOMPSAT-2A), scheduled for launch in early 2018, is an example of these sensors. This paper introduces operational prototype algorithms that attempt to produce QPN products for GEO-KOMPSAT-2A. The AMI QPN products include the potential accumulated rainfall and the probability of rainfall (PoR) for a 3-h lead time. The potential accumulated rainfall algorithm consists of two major procedures: 1) identification of rainfall features on the outputs from the GEO-KOMPSAT-2A rainfall rate algorithm; and 2) tracking of these rainfall features between two consecutive images. The potential accumulated rainfall algorithm extrapolates precipitation fields every 15 min. Rainfall rates at each time step are accumulated to yield the 3-hourly rainfall. In addition, the extrapolated precipitation fields at 15-min intervals are used as inputs for the PoR algorithm, which produces the probability of precipitation during the same 3-h period. The QPN products can be classified as extrapolated features associated with precipitation. The validation results show that the extrapolated features tend to meet the designated accuracy for the prototype development stage. We also confirm a tendency for decreasing accuracy of the QPN products with increasing forecast lead time. Mitigating the dependence on lead time may remain a challenge that can be incorporated into the next generation of QPN algorithms.
关键词： probability of rainfall (PoR),quantitative precipitation nowcast,Geostationary satellite,potential accumulated rainfall
更新于2025-09-23 15:19:57
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Combinatorial Treatment of Human Cardiac Engineered Tissues With Biomimetic Cues Induces Functional Maturation as Revealed by Optical Mapping of Action Potentials and Calcium Transients
摘要： Although biomimetic stimuli, as microgroove-induced alignment (μ), triiodothyronine (T3) induction, and electrical conditioning (EC), have been reported to promote maturation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), a systematic examination of their combinatorial effects on engineered cardiac tissue constructs and the underlying molecular pathways has not been reported. Herein, human embryonic stem cell-derived ventricular cardiomyocytes (hESC-VCMs) were used to generate a micro-patterned human ventricular cardiac anisotropic sheets (hvCAS) for studying the physiological effects of combinatorial treatments by a range of functional, calcium (Ca2+)-handling, and molecular analyses. High-resolution optical mapping showed that combined μ-T3-EC treatment of hvCAS increased the conduction velocity, anisotropic ratio, and proportion of mature quiescent-yet-excitable preparations by 2. 3-, 1. 8-, and 5-fold (>70%), respectively. Such electrophysiological changes could be attributed to an increase in inward sodium current density and a decrease in funny current densities, which is consistent with the observed up- and downregulated SCN1B and HCN2/4 transcripts, respectively. Furthermore, Ca2+-handling transcripts encoding for phospholamban (PLN) and sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) were upregulated, and this led to faster upstroke and decay kinetics of Ca2+-transients. RNA-sequencing and pathway mapping of the TGF-β signaling was downregulated; the TGF-β receptor agonist and antagonist TGF-β1 and SB431542 partially reversed T3-EC induced quiescence and reduced spontaneous contractions, respectively. Taken together, we concluded that topographical cues alone primed cardiac tissue constructs for augmented electrophysiological and calcium handling by T3-EC. Not only do these studies improve our understanding of hPSC-CM biology, but the orchestration of these pro-maturational factors also improves the use of engineered cardiac tissues for in vitro drug screening and disease modeling.
关键词： triiodothyronine,calcium handling,electrical conditioning,tissue engineering,maturation,action potential
更新于2025-09-23 15:19:57
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Highly Reproducible and Efficient FASnI <sub/>3</sub> Perovskite Solar Cells Fabricated with Volatilizable Reducing Solvent
摘要： Lead-free tin halide perovskite solar cells (PSCs) have attracted great attention because of their low toxicity, ideal band gap, and high carrier mobilities. However, the efficiency and reproducibility of tin halide PSCs has been limited because of the facile oxidation of Sn2+ to Sn4+. Herein, liquid formic acid (LFA) was introduced as a reducing solvent in the FASnI3 (FA: formamidinium) perovskite precursor solution. Unlike solid reducing additives, the LFA solvent is volatile, so no residual LFA remained in the FASnI3 perovskite film. Use of the LFA solvent resulted in production of the FASnI3 perovskite film with high crystallinity, low Sn4+ content, reduced background doping, and low electronic trap density. As a result, an efficiency of over 10% was obtained for lead-free tin halide PSCs with improved reproducibility.
关键词： tin,Lead-free,oxidation,trap density,standard reduction potential
更新于2025-09-23 15:19:57
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Non-parabolic potential dependence of optical second harmonic generation from the Si(111) electrode/electrolyte interface
摘要： We performed potential dependent second harmonic generation (SHG) measurements on the Si(111) electrolyte interface at different azimuthal angles and for different polarization combinations. When the external potential was biased from the equilibrium potential to the flatband potential (Efb), the SHG intensity decreased linearly with the potential when the azimuthal angle was oriented at 301. This linearity extends well beyond the linear region of the Mott–Schottky plot as measured traditionally by capacitance measurements. When the external potential was scanned from Efb toward more negative potentials, the response of SHG intensity showed quadratic behavior and can be described by the parabolic model. The non-parabolic potential dependence cannot be explained with the parabolic model proposed from previous literature. Such asymmetric behavior only implied that the interfacial structure of the Si(111) electrode changes from semiconductor to metal with the applied electric potential biased negatively, i.e. with accumulation of electrons in the surface region. The anisotropic contribution from the Si(111) electrode can also significantly affect the SHG response as seen where the minimum of the potential dependent SHG curve shifts away from Efb.
关键词： potential dependence,Si(111) electrode,electrolyte interface,non-parabolic behavior,second harmonic generation
更新于2025-09-23 15:19:57
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Can Realistic Liver Tissue Surrogates Accurately Quantify the Impact of Reduced-kV Imaging on Attenuation and Contrast of Parenchyma and Lesions?
摘要： To assess if a liquid tissue surrogate for the liver (LTSL) can emulate contrast-enhanced liver parenchyma and lesions and quantify the impact of reduced-kV imaging as a function of lesion contrast, phase of enhancement, and phantom size.
关键词： Liquid tissue surrogate,Computed tomography,Lesion,Tube potential,Liver
更新于2025-09-19 17:15:36
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Effects of site asymmetry and valley mixing on Hofstadter-type spectra of bilayer graphene in a square-scatter array potential
摘要： Under a magnetic field perpendicular to an monolayer graphene, the existence of a two-dimensional periodic scatter array can not only mix Landau levels of the same valley for displaying split electron-hole Hofstadter-type energy spectra, but also couple two sets of Landau subbands from different valleys in a bilayer graphene. Such a valley mixing effect with a strong scattering strength has been found observable and studied thoroughly in this paper by using a Bloch-wave expansion approach and a projected 2 × 2 effective Hamiltonian including interlayer coupling and asymmetrical on-site energies due to a vertically-applied electric field. For bilayer graphene, we find two important characteristics, i.e., mixing and interference of intervalley scatterings in the presence of a scatter array, as well as a perpendicular-field induced site-energy asymmetry which deforms severely or even destroy completely the Hofstadter-type band structures due to the dependence of Bloch-wave expansion coefficients on the applied electric field.
关键词： bilayer graphene,valley mixing,Hofstadter spectrum,site asymmetry,scatter array potential
更新于2025-09-19 17:15:36
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Efficient and accurate calculation of band gaps of halide perovskites with the Tran-Blaha modified Becke-Johnson potential
摘要： We report on a reoptimization of the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential dedicated to the prediction of the band gaps of three-dimensional (3D) and layered hybrid organic-inorganic perovskites (HOPs) within pseudopotential-based density functional theory methods. These materials hold promise for future photovoltaic and optoelectronic applications. We begin by determining a set of parameters for 3D HOPs optimized over a large range of materials. Then we consider the case of layered HOPs. We design an empirical relationship that facilitates the prediction of band gaps of layered HOPs with arbitrary interlayer molecular spacers with a computational cost considerably lower than that of more advanced methods like hybrid functionals or GW. Our study also shows that substituting interlayer molecular chains of layered HOPs with Cs atoms is an appealing and cost-effective route to band gap calculations. Finally, we discuss the pitfalls and limitations of TB-mBJ for HOPs, notably its tendency to overestimate the effective masses due to the narrowing of the band dispersions. We expect our results to extend the use of TB-mBJ for other low-dimensional materials.
关键词： Tran-Blaha modified Becke-Johnson potential,halide perovskites,computational methods,band gaps,density functional theory,hybrid organic-inorganic perovskites,pseudopotential
更新于2025-09-19 17:15:36
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[IEEE 2018 11th Biomedical Engineering International Conference (BMEiCON) - Chiang Mai, Thailand (2018.11.21-2018.11.24)] 2018 11th Biomedical Engineering International Conference (BMEiCON) - Self-Flickering Visual Stimulus based on Visual illusion for SSVEP-based BCI System
摘要： This paper proposes the use of the windmill pattern visual stimulus to induce human vision by employing a phenomenon of visual illusion for steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) system. We had to explore the brain response to the flickering pattern as windmill pattern, three BCI commands can be generated by using three different windmill patterns. SSVEP technique was used to detect the response. The average accuracy of classification was approximately 80.5%. With the proposed visual stimulus pattern, it can reduce eye fatigue and increase the number of commands for the existing SSVEP-based BCI. Therefore, the proposed visual stimulus pattern can be used for practical BCI applications
关键词： Steady-state visual evoked potential,Brain-computer interface,Visual illusion
更新于2025-09-19 17:15:36