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Typically n-i-p structured perovskite solar cells (PSCs) incorporate 2,2′,7,7′-tetrakis (N,N-di-p-methoxyphenyl amine)-9,9′-spirobifluorene (spiro-OMeTAD) as the hole-transporting material. Chemical doping of spiro-OMeTAD involves a lithium bis(trifluoromethyl sulfonyl)imide dopant, causing complex side-reactions that affect the device performance, which are not fully understood. Here, we investigate the aging-dependent device performance of widely used formamidinium lead triiodide (FAPbI3)-based PSCs correlated with lithium-ion (Li+) migration. Comprehensive analyses reveal that Li+ ions migrate from spiro-OMeTAD to perovskite, SnO2, and their interfaces to induce the phase-back conversion of α-FAPbI3 to δ-FAPbI3, generation and migration of iodine defects, and de-doping of spiro-OMeTAD. The rapid performance drop of FAPbI3-based PSCs, even aging under dark conditions, is attributed to a series of these processes. This study identifies the hidden side effects of Li+ ion migration in FAPbI3-based PSCs that can guide further work to maximize the operational stability of PSCs.

State-of-the-art wide bandgap perovskite compositions for perovskite/silicon tandem solar cells often incorporate methylammonium (MA) containing multi-cation-mixed-halides compositions to achieve high efficiency. However, the MA-containing perovskite films and devices are likely to suffer from photo and thermal instability due to volatile MA + cations. Here, systematic investigation on MA-free FA 1– x Cs x PbI 3– y Br y perovskite compositions was conducted to devise an effective MA-free wide bandgap composition. The Cs + content was found to play a central role in optimizing the purity and stability of the desired perovskite phase. With varying Cs + contents, a trade-off between structural formability of the perovskite phase and lattice microstrain was observed. Balancing the sacrificial trade-off was found to be critical in minimizing the trap densities to achieve high performance and stable wide bandgap perovskite solar cells. Our findings provide insights into the development of an optimal perovskite composition for high efficiency and stable perovskite-based tandem solar cells.

Cations with suitable sizes to occupy an interstitial site of perovskite crystals have been widely used to inhibit ion migration and promote the performance and stability of perovskite optoelectronics. However, such interstitial doping inevitably leads to lattice microstrain that impairs the long-range ordering and stability of the crystals, causing a sacrificial trade-off. Here, we unravel the evident influence of the valence states of the interstitial cations on their efficacy to suppress the ion migration. Incorporation of a trivalent neodymium cation (Nd 3+ ) effectively mitigates the ion migration in the perovskite lattice with a reduced dosage (0.08%) compared to a widely used monovalent cation dopant (Na + , 0.45%). The photovoltaic performances and operational stability of the prototypical perovskite solar cells are enhanced with a trace amount of Nd 3+ doping while minimizing the sacrificial trade-off. Ion migration has a detrimental effect on the performance and stability of halide perovskite optoelectronics. Here, the authors incorporated a small dosage of high-valence neodymium cation to suppress this, with a minimal impact on the lattice microstrain.

We present a digital-to-analog converter (DAC) with full-swing DAC output and a proposed half-power supply calibration technique. To generate a full-swing DAC output, symmetric thermometer decoders and an output selector are implemented to select the appropriate current cell according to the output voltage range. Furthermore, to improve the linearity, we propose a half-power supply calibration circuit consisting of comparators and calibration counters to control the current of the current cells at the half-power supply voltage point, where the voltage mismatch typically occurs. The DAC was fabricated in a 28 nm CMOS process, with a full chip area of 0.95 mm × 0.93 mm. The measurement results demonstrate a maximum voltage mismatch improvement of 95% when using the proposed half-power supply calibration technique, with DNL and INL values of 0.39 and 1.15 LSB. The total power consumption was 73.8 mW at 100 MSPS, with analog and digital supply voltages of 1.8 and 1.0 V, respectively.

Typically n‐i‐p structured perovskite solar cells (PSCs) incorporate 2,2′,7,7′‐tetrakis ( N , N ‐di‐ p ‐methoxyphenyl amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) as the hole‐transporting material. Chemical doping of spiro‐OMeTAD involves a lithium bis(trifluoromethyl sulfonyl)imide dopant, causing complex side‐reactions that affect the device performance, which are not fully understood. Here, we investigate the aging‐dependent device performance of widely used formamidinium lead triiodide (FAPbI 3 )‐based PSCs correlated with lithium‐ion (Li + ) migration. Comprehensive analyses reveal that Li + ions migrate from spiro‐OMeTAD to perovskite, SnO 2 , and their interfaces to induce the phase‐back conversion of α‐FAPbI 3 to δ‐FAPbI 3 , generation and migration of iodine defects, and de‐doping of spiro‐OMeTAD. The rapid performance drop of FAPbI 3 ‐based PSCs, even aging under dark conditions, is attributed to a series of these processes. This study identifies the hidden side effects of Li + ion migration in FAPbI 3 ‐based PSCs that can guide further work to maximize the operational stability of PSCs. image

Europium (Eu) has two naturally stable isotopes ( 151 Eu and 153 Eu). The Eu anomalies produced by feldspar crystallization during magma differentiation have provided valuable geochemical information for understanding the evolutionary history of magma in the crust-mantle system. Recently, the correlation between the degree of Eu isotope fractionation (δ 153 Eu) and the magnitude of the Eu anomaly produced by magma differentiation has received much attention as a new research field for understanding the evolution of the Earth system 1 , 2 , 3 – 4 . Here, we report large variation of Eu isotope ratio for geochemically mafic volcanic rocks from the Korean Peninsula and Ocean Drilling Program (ODP) site 801 C, western Pacific Ocean. The Eu isotope ratio in this work was determined precisely via multicollector inductively coupled plasma mass spectrometry using a Sm internal standard 5 , 6 – 7 . We find that the δ 153 Eu values of hydrothermally altered alkaline mafic volcanic rocks vary from − 0.65‰ to -0.1‰, in contrast to the narrow range that characterizes the primary fresh subalkaline mafic volcanic rocks (from − 0.1‰ to 0.1‰). Our findings indicate that Eu isotope fractionation can occur through not only magmatic differentiation but also hydrothermal reactions in the Earth system.

Among many available biometrics identification methods, finger-vein recognition has an advantage that is difficult to counterfeit, as finger veins are located under the skin, and high user convenience as a non-invasive image capturing device is used for recognition. However, blurring can occur when acquiring finger-vein images, and such blur can be mainly categorized into three types. First, skin scattering blur due to light scattering in the skin layer; second, optical blur occurs due to lens focus mismatching; and third, motion blur exists due to finger movements. Blurred images generated in these kinds of blur can significantly reduce finger-vein recognition performance. Therefore, restoration of blurred finger-vein images is necessary. Most of the previous studies have addressed the restoration method of skin scattering blurred images and some of the studies have addressed the restoration method of optically blurred images. However, there has been no research on restoration methods of motion blurred finger-vein images that can occur in actual environments. To address this problem, this study proposes a new method for improving the finger-vein recognition performance by restoring motion blurred finger-vein images using a modified deblur generative adversarial network (modified DeblurGAN). Based on an experiment conducted using two open databases, the Shandong University homologous multi-modal traits (SDUMLA-HMT) finger-vein database and Hong Kong Polytechnic University finger-image database version 1, the proposed method demonstrates outstanding performance that is better than those obtained using state-of-the-art methods.

Background One of the main objectives of the molecular evolution and evolutionary systems biology field is to reveal the underlying principles that dictate protein evolutionary rates. Several studies argue that expression abundance is the most critical component in determining the rate of evolution, especially in unicellular organisms. However, the expression breadth also needs to be considered for multicellular organisms. Results In the present paper, we analyzed the relationship between the two expression variables and rates using two different genome-scale expression datasets, microarrays and ESTs. A significant positive correlation between the expression abundance (EA) and expression breadth (EB) was revealed by Kendall's rank correlation tests. A novel random shuffling approach was applied for EA and EB to compare the correlation coefficients obtained from real data sets to those estimated based on random chance. A novel method called a Fixed Group Analysis (FGA) was designed and applied to investigate the correlations between expression variables and rates when one of the two expression variables was evenly fixed. Conclusions In conclusion, all of these analyses and tests consistently showed that the breadth rather than the abundance of gene expression is tightly linked with the evolutionary rate in multicellular organisms.

When images are acquired for finger-vein recognition, images with nonuniformity of illumination are often acquired due to varying thickness of fingers or nonuniformity of illumination intensity elements. Accordingly, the recognition performance is significantly reduced as the features being recognized are deformed. To address this issue, previous studies have used image preprocessing methods, such as grayscale normalization or score-level fusion methods for multiple recognition models, which may improve performance in images with a low degree of nonuniformity of illumination. However, the performance cannot be improved drastically when certain parts of images are saturated due to a severe degree of nonuniformity of illumination. To overcome these drawbacks, this study newly proposes a generative adversarial network for the illumination normalization of finger-vein images (INF-GAN). In the INF-GAN, a one-channel image containing texture information is generated through a residual image generation block, and finger-vein texture information deformed by the severe nonuniformity of illumination is restored, thus improving the recognition performance. The proposed method using the INF-GAN exhibited a better performance compared with state-of-the-art methods when the experiment was conducted using two open databases, the Hong Kong Polytechnic University finger-image database version 1, and the Shandong University homologous multimodal traits finger-vein database.

Biometrics is a method of recognizing a person based on one or more unique physical and behavioral characteristics. Since each person has a different structure and shape, it is highly secure and more convenient than the existing security system. Among various biometric authentication methods, finger-vein recognition has advantages in that it is difficult to forge because a finger-vein exists inside one’s finger and high user convenience because it uses a non-invasive device. However, motion and optical blur may occur for some reasons such as finger movement and camera defocusing during finger-vein recognition, and such blurring occurrences may increase finger-vein recognition error. However, there has been no research on finger-vein recognition considering both motion and optical blur. Therefore, in this study, we propose a new method for increasing finger-vein recognition accuracy based on a network for the restoration of motion and optical blurring in a finger-vein image (RMOBF-Net). Our proposed network continuously maintains features that can be utilized during motion and optical blur restoration by actively using residual blocks and feature concatenation. Also, the architecture RMOBF-Net is optimized to the finger-vein image domain. Experimental results are based on two open datasets, the Shandong University homologous multi-modal traits finger-vein database and the Hong Kong Polytechnic University finger-image database version 1, from which equal error rates of finger-vein recognition accuracy of 4.290–5.779% and 2.465–6.663% were obtained, respectively. Higher performance was obtained from the proposed method compared with that of state-of-the-art methods.