Machine Learning Optimization of p-Type Transparent Conducting Films

p-Type transparent conducting materials (p-TCMs) are important components of optoelectronic devices including solar cells, photodetectors, displays, and flexible sensors. Cu-Zn-S thin films prepared by chemical bath deposition (CBD) can have both high transparency in the visible range (>80%) as well as excellent hole conductivity (>1000 S cm-1). However, the interplay between the deposition parameters in the CBD process (metal and sulfur precursor concentrations, temperature, pH, complexing agents, etc.) creates a multidimensional parameter space such that optimization for a specific application is challenging and time-consuming. Here we show that strategic design of experiment combined with machine learning (ML) allows for the efficient optimization of p-TCM performance. The approach is guided by a figure of merit (FOM) calculated from the film conductivity and optical transmission in the desired spectral range. A specific example is shown using two steps of optimization using a selected subset of four experimental CBD factors. The ML model is based on support vector regression employing a radial basis function as the kernel function. 10-fold cross-validation was performed to mitigate overfitting. After the first round of optimization, predicted areas in the parameter space with maximal FOMs were selected for a second round of optimization. Films with optimal FOMs were incorporated into heterojunction solar cells and transparent photodiodes. The optimization approach shown here will be generally applicable to any materials synthesis process with multiple parameters

Understanding the role of nanostructuring in photoelectrode performance for light driven water splitting

The analysis of capacitance data for regular nanostructured photoelectrodes is revisited using a hematite nanorod array as an example. The effects of the cylindrical nanorod geometry on the capacitance voltage behaviour are outlined, and the limiting case of complete depletion is discussed in terms of the residual geometric capacity at the base of the nanorods. Since nanorod arrays generally leave areas of the substrate exposed, it is necessary to consider the parallel capacitance associated with the fraction of uncovered surface. The sensitivity of the capacitance fitting to parameter variation is explored. The enhancement of external quantum efficiency EQE by nanostructuring is also discussed using hematite nanorod arrays as experimental examples. It is shown that, although very substantial EQE enhancement should be achieved by simple geometric effects, the performance of nanostructured hematite electrodes in the visible region of the spectrum is considerably lower than predicted if all charge carriers generated in the space charge region SCR were collected. Further analysis reveals that the internal quantum efficiency increases with photon energy, suggesting that the probability of generating free, rather than bound, electron hole pairs in hematite depends on the excess energy hv Ega

Si photocathode with Ag-supported dendritic Cu catalyst for CO2 reduction

Si photocathodes integrated with Ag-supported dendritic Cu catalysts are used to perform light-driven reduction of CO2 to C2 and C3 products in aqueous solution. A back illumination geometry with an n-type Si absorber was used to permit the use of absorbing metallic catalysts. Selective carrier collection was accomplished by a p+ implantation on the illumination side and an n+ implantation followed by atomic layer deposition of TiO2 on the electrolyte site. The Ag-supported dendritic Cu CO2 reduction catalyst was formed by evaporation of Ag followed by high-rate electrodeposition of Cu to form a high surface area structure. Under simulated 1 sun illumination in 0.1 M CsHCO3 saturated with CO2, the photovoltage generated by the Si (∼600 mV) enables C2 and C3 products to be produced at -0.4 vs. RHE. Texturing of both sides of the Si increases the light-limited current density, due to reduced reflection on the illumination side, and also deceases the onset potential. Under simulated diurnal illumination conditions photocathodes maintain over 60% faradaic efficiency to hydrocarbon and oxygenate products (mainly ethylene, ethanol, propanol) for several days. After 10 days of testing, contamination from the counter electrode is observed, which causes an increase in hydrogen production. This effect is mitigated by a regeneration procedure which restores the original catalyst selectivity. A tandem, self-powered CO2 reduction device was formed by coupling a Si photocathode with two series-connected semitransparent CH3NH3PbI3 perovskite solar cells, achieving an efficiency for the conversion of sunlight to hydrocarbons and oxygenates of 1.5% (3.5% for all products)

IODINE STATUS OF PREGNANT WOMEN RESIDING IN URBAN SLUMS IN DELHI

Objectives: The present study was carried out to determine the iodine nutrition status among pregnant women in slums of West Delhi.Methods: A community-based cross-sectional study was carried out among the third-trimester pregnant women residing in urban slums of West Delhi. Urinary iodine concentration was estimated using ammonium persulfate method, and salt iodine was estimated using iodometric titration.Results: Of the total 180 pregnant women, 70.6% were consuming adequately iodized salt (iodine levels ≥15 ppm). Median urinary iodine level for the pregnant women was 147.5 μg/L indicating iodine deficiency among this group. A total of 51.1% of women had urinary iodine levels <150 μg/L.Conclusion: Pregnant women belonging to slum community from Delhi have a suboptimal iodine status. Further, the proportion of women consuming iodized salt is less than the national average indicating the need to educate these women about the importance of iodine during pregnancy

ANEMIA AND VITAMIN B12 DEFICIENCY IN ELDERLY.

 Objective: The present study was carried out to assess the prevalence of anemia, vitamin B12 deficiency and hyperhomocysteinemia among elderly in slums of West Delhi.Methods: A cross-sectional study was carried out among 234 elderly aged 60 and above in slums of West Delhi. 5 ml blood was collected from 116 elderly and was analyzed for hemoglobin, Vitamin B12 and homocysteine. Anemia was defined as hemoglobin <130 g/L and <120 g/l for male and female, respectively, Vitamin B12 deficiency as serum Vitamin B12 <203 pg/ml and hyperhomocysteinemia as serum homocysteine >15 μmol/l.Results: The overall prevalence of anemia, Vitamin B12 deficiency, and hyperhomocysteinemia among elderly was 57.76%, 36.36%, and 57.57%, respectively. Among anemic elderly, 33.33% and 64.15% had Vitamin B12 deficiency and hyperhomocysteinemia, respectively.Conclusion: More than half of the elderly population was anemic, while one-third was having Vitamin B12 deficiency

PREVALENCE OF HYPERTENSION AMONG ADULT POPULATION IN SLUMS OF WEST DELHI

Objective: The present study was conducted to assess the prevalence of hypertension in adult population residing in slums of West Delhi.Methods: A cross-sectional study was conducted among adult population of 18-59 years residing in urban slums of West Delhi. Blood pressure was measured using digital machine (OMRON). The data obtained were analyzed for percent prevalence, mean, standard deviation, and median. Joint National Committee (JNC)on prevention, detection, evaluation, and treatment of high blood pressure (JNC)VI and JNC VII criteria were used to classify hypertension.Results: The overall prevalence of hypertension was 25.3%. The prevalence was higher (27.9%)in males than females (22.8%)and also in the age group 46-59 years (43.0%)as compared to 18-45 years (19.8%). The overall prevalence of prehypertension, Stage I and Stage II hypertension, respectively, was 35.2%, 16.1% and 9.2%.Conclusion: A one-fourth of the adult population is hypertensive. Early diagnosis and treatment are advisable, besides awareness about dietary and lifestyle modification

Hematite Nanorod Electrodes Modified with Molybdenum: Photoelectrochemical Studies

The preparation of hematite nanorod electrodes modified with molybdenum and their photoelectrochemical behavior for water photooxidation have been addressed in the quest for improved electrodes for water splitting. The hematite nanorods were synthesized through chemical bath deposition, and Mo was added by following two variants of a drop-casting method based on ammonium heptamolybdate solutions. FE-SEM, TEM, XRD, and XPS were employed for electrode structural and morphological characterization. The reported results reveal that the impregnation method does not cause significant changes in the hematite structure and nanorod morphology. Importantly, the modification with Mo triggers a significant improvement in the photoactivity of the electrodes, obtaining a photocurrent increase of up to 43×. A specific Mott−Schottky analysis applicable to nanostructured electrodes was performed, revealing that the modification with Mo leads to an increase in electron concentration and to a shift of the flat band potential toward more positive values. A second role of Mo as a passivating agent needs to be invoked to explain the experimental observations. It is worth noting that this modification method allows precise control of the amount of Mo contained in the samples while maintaining the morphology of the electrode.We are grateful to the Spanish MINECO for financial support through projects MAT2012-37676 and MAT2015-71727-R both supported with FEDER funds. A.C. thanks the Vicepresidency of Research, Development and Innovation of University of Alicante for financial support through an initiation research grant. D.C. is also grateful to MINECO for the award of an FPI grant